JP3712392B2 - Manufacturing method and authentication method of card on which digital information is printed using digital watermark technology, and apparatus thereof - Google Patents

Description

【００３２】
数１において、ｓは元の信号値であり、ｔは変換された信号値であり、Ｎは信号の長さを示し、係数ｃは下記の数２のように定義される。
【００３３】
【数２】

【００３４】
（但し、１≦ｋ≦Ｎ−１の場合である）。
また、正方行列に対する２次元ＤＣＴ変換は、下記の数３のように定義される。
【００３５】
【数３】

【００３６】
前記数３において、Ｎ、ｓ、ｔは、１次元ＤＣＴ変換におけると同意義であり、ｃ（ｉ，ｊ）は、下記の数４のように定義される。
【００３７】
【数４】

【００３８】
（但し、ｉ≠０、ｊ≠０の場合である）。
また、ＤＣＴ変換は逆変換を有し、１次元及び２次元に対しそれぞれ下記の数５及び数６のように定義される。
【００３９】
【数５】

【００４０】
【数６】

【００４１】
次に、ＤＷＴ変換について説明する。フーリエ変換が正弦関数と余弦関数を基底関数として用いる変換であれば、ウェーブレット変換は基底関数としてウェーブレットを用いる変換であって、連続ウェーブレット変換及び離散ウェーブレット変換に大別される。連続ウェーブレット変換は、下記の数７のように表される。
【数７】

【００４２】
前記数７において、ｓはスケーリングを、τは位置移動（ｔｒａｎｓｌａｔｉｏｎ）を示し、Ψ（ｓ，ｔ）はスケーリングされて位置移動された形態のウェーブレットをそれぞれ示す。
【００４３】
スケーリングは、周波数と関連し、低いスケーリング、即ち圧縮されたウェーブレットは高周波成分を抽出し、高いスケーリング、即ち拡張されたウェーブレットは低周波成分を抽出する。通常、連続ウェーブレット変換は、変換により得られるウェーブレット係数が、スケーリングと位置移動の関数として無限に得られるため、実際の具現が不可能である。
【００４４】
従って、スケーリングと位置移動に対し一定の周波数領域のみを選択する離散ウェーブレット変換を用いると、より効果的に具現することができる。しかし、離散ウェーブレット変換もまた、コンピュータで具現するには多大な演算量による負担が伴われるので、高速ウェーブレット変換であるフィルターバンクを用いて画像イメージを変換させることが好ましい。この方法は、古典的な２チャネルサブバンドコーディング及びピラミッドアルゴリズムを用い、逆変換のためのフィルターバンク間の関係（ＰＲ−ＱＭＦ：Ｐｅｒｆｅｃｔｌｙ ｒｅｃｏｎｓｔｒｕｃｔｉｏｎ ｑｕａｄｒａｔｕｒｅ ｍｉｒｒｏｒ ｆｉｌｔｅｒ）さえ成立すれば、簡単に具現することができるという長所がある。
【００４５】
前記透かし生成部４０は、カード情報データベース２０から所定のユーザキーが入力され、ユーザキーから透かしを生成する。ユーザキーを透かしに用いると、検出した透かしとユーザキーから生成した透かしとの間の相関関係により、デジタル画像の真偽や変更の有無をより正確に判断することができ、透かしの保安性を強化させるという長所がある。
【００４６】
また、ユーザキーから透かしとして用いられる疑似乱数を発生させる前に、ユーザが暗号化器４１を用いて該ユーザキーを暗号化した後、この暗号化したキーを入力され、疑似乱数生成器４２により疑似乱数を発生させる。ユーザキーが暗号化ステップを経ると、ユーザキー値が容易に変形されないだけでなく、ユーザキーそのものを隠匿することができるので、暗号化したユーザキーから生成した透かしをデジタル画像に埋め込むと、その後、デジタル画像から透かしを検出するときにユーザキーそのものが公開される恐れがないという長所がある。暗号化は、通常の暗号化方式、例えば、ＤＥＳ（ｄａｔａ ｅｎｃｒｙｐｔｉｏｎ ｓｔａｎｄａｒｄ）方式、ＲＳＡ方式、ＥＣＣ方式等を用いることができる。本発明では、暗号化するデータがコーディングされ、その結果が疑似乱数（ｐｓｅｕｄｏ ｒａｎｄｏｍ ｎｕｍｂｅｒ）として出力される、ＰＮ−ｃｏｄｅ方式を用いている。
【００４７】
このようにして透かしが生成すると、透かし埋込器１３０により、下記の数学数５による方式のプロセスを経てデジタル画像に埋め込まれる（ステップＳ２３０₁またはＳ２３０₂）。
【００４８】
【数８】

【００４９】
ここで、ｆｘは、デジタル画像に埋め込まれる透かしの強度を調整するための特性関数である。ｆｘは、多様に設定することができ、デジタル画像の周波数領域変換係数（ＦＯＩ）の一部をモジュロ（ｍｏｄｕｌｏ）演算しまたは多数の変換係数の平均、標準偏差、分散等の統計的特性値を取り出す関数であってもよい。
【００５０】
ＦＯＩ’は、デジタル画像の周波数領域変換係数（ＦＯＩ）に特性関数ｆｘを適用した値に透かし（Ｗ）が掛けられた結果を示す。数５における変換係数（ＦＯＩ）は、デジタル画像の周波数領域の値であるため、２次元配列の形態であり、透かし（Ｗ）は、１次元順列（ｓｅｑｕｅｎｃｅ）の形態を有するため、変換係数（ＦＯＩ）を順列の形態にし、または透かし（Ｗ）を２次元ブロック化して演算する。演算のために、画像の周波数係数毎に一つの透かしをマッチングして計算することもでき、複数の画像の周波数係数の統計的な特性を得て、一つの透かしと演算する方法がある。
【００５１】
次に、数８を参考して、透かしが埋め込まれるステップについて詳述する。
前記透かし埋込器１３０は、所定の特定周波数領域の変換係数（以下、埋込係数という）の絶対値に特性関数ｆｘを適用して得た値と透かしを掛けた結果（ＦＯＩ’、以下、代置係数という）を、他の所定の特定周波数領域の変換係数と代置（ｒｅｐｌａｃｅｍｅｎｔ）するプロセスを行う。例えば、デジタル画像を低周波数と中間周波数と高周波数との領域に分けたとき、デジタル画像の情報が相対的に少なく含まれた中間周波数領域または高周波数領域に透かしを埋め込むことになり、低周波数領域の変換係数（埋込係数）に特性関数ｆｘを適用した値に透かしを掛けた結果（代置係数）で、既存の中間周波数領域や高周波数領域の変換係数を代置することにより、透かしの埋込みが完了する。
【００５２】
このような方式によると、高周波数部分の一部を捨てる圧縮ステップやぼかし（ｂｌｕｒｒｉｎｇ）のような変形があったとしても、透かしは、低周波数領域の係数と掛けられて高周波数領域に代置されるものであり、変形後も高周波数領域が相当部分残るようになるため、変形に強いという長所がある。
【００５３】
本明細書では、透かしが、低周波数領域の係数の絶対値に特性関数ｆｘを適用した結果と掛けられ、中間周波数領域と高周波数領域の間に代置されることを一例として示しているが、デジタル画像の品質を低下させない範囲の周波数領域を選択して透かしを埋め込こんでもよい。例えば、高周波領域の変換係数の絶対値に特性関数を適用した結果に透かしを掛けた後、高周波数領域に代置することができるので、周波数領域に変換されたデジタル画像に透かしを埋め込む方法はこれに限らず、多様な周波数領域においても応用され得る。
【００５４】
また、本発明は、印刷により画像の全体的な特徴があまり変わらない点に着目し、任意の周波数領域の係数で他の周波数領域の係数を補償することにより、画像の全体的な特性に変化を与えないとの周波数領域の特性を用いれば、印刷に強い特徴を有するようになるので、印刷等により透かしが消えてしまうことを防止することができる。また、上述した周波数領域の特性を用いた透かしの埋込法によると、透かしを埋め込んでもデジタル画像の全体的な特性が変わらないため、即ちデジタル画像の原本の品質が低下しないため、印刷後にもデジタル画像の原本の品質を鑑賞することができる。
【００５５】
数８において、デジタル画像に透かしが埋め込まれたとき、透かしの強度の強さを調整するものはｆｘ関数である。この特性関数値は、ユーザが任意に設定することができるので、いかなる値も可能であり、特に透かし（Ｗ）の埋込みによるデジタル画像の品質が低下しないように適切な関数で決定することができる。即ち、透かしの強度の強さとデジタル画像の品質の変形は、互いに反比例の関係であるため、透かしの使用環境とデジタル画像の品質維持の側面とを考慮して決めることが好ましい。
【００５６】
次に、透かしが埋め込まれたデジタル画像を得るため、逆周波数領域変換器１４０は、周波数領域に変換されたデジタル画像を復元させる（ステップＳ２４０₁またはＳ２４０₂）。前記周波数領域変換器１２０がＤＣＴ変換やＤＷＴ変換またはＦＦＴ変換を用いた場合、逆周波数領域変換器１４０は、逆ＤＣＴ変換や逆ＤＷＴ変換または逆ＦＦＴ変換を用いる。ここで、デジタル画像がカラー画像である場合は、逆カラーモデル変換器１５０により、逆周波数領域変換が行われた輝度成分と、周波数領域変換が行われなかった輝度成分を除いた残りの成分を用い、ＨＳＢモード、ＹＩＱモードまたはＹＣｂＣｒモードのカラーモデルから元のカラーモデルに復元される（ステップＳ２４５）。最後に、透かしが埋め込まれたデジタル画像を得ることにより、透かしのデジタル画像への埋込みプロセスが終了する（ステップＳ２５０）。
【００５７】
このようにして、デジタル画像に対する透かしの埋込みステップが終了すると、カードの原資材にデジタル画像印刷部６０からカードの表面に印刷して透かしが埋め込まれたカードを製作することができる。
【００５８】
このように製作された本発明による透かしが埋め込まれたカードにおいて、埋め込まれた透かしは位置や内容により多様に決められ得る。透かしの内容が文字や数字またはイメージであるか、または透かしが埋め込まれる位置がカードの全体または一部であるかは、カード製作／発給者が選択する透かし技法の特徴により多様に決められる。例えば、上述した透かしが埋め込まれたカードの製作ステップにおいて、透かしを埋め込む部分がカード発給者の写真である場合、先ず、写真が印刷される所定の空間を空白として残し、写真の他にカードに印刷される情報のみをカードの原資材に印刷してから、カード発給申請者の写真をデジタル画像で製作し、このデジタル画像にのみ透かしを埋め込んだ後、透かしが埋め込まれたデジタル画像をカードの原資材の所定の位置に印刷してもよい。これに対し、透かしを埋め込む部分がカード全体であれば、カードに印刷される情報をカードの原資材全体のサイズと同一のサイズのデジタル画像に製作した後、このデジタル画像に透かしを埋め込んでから、カードの原資材に印刷してもよい。または、透かしがカードに印刷されるイメージの特定の部分に埋め込まれる場合は、透かしが埋め込まれる部分に特定の識別子を表示する方法を用いてもよい。
【００５９】
以下、図５乃至図８を参照して、このような製作ステップを経て作られた透かしが埋め込まれたカードに対する認証のための装置とその方法について説明する。透かしが埋め込まれたカードを認証するステップ及び装置は、上述したカードの製作ステップ及びその装置に対応するように構成され、透かしが埋め込まれたカードを認証するステップで用いられる透かしの検出技法は、透かしが埋め込まれたカードの製作ステップで用いられる透かしの埋込技法に対応する。
【００６０】
図５は、図１におけるカード製作装置により製作されたカードを認証するためのカード認証装置の構成を示すブロック図である。図５におけるカード認証装置２００は、ユーザキーを入力されて透かしを生成する部分と、カードそのものに記録された情報を処理する部分に大別される。カードそのものに記録された情報とは、カードの表面に印刷されたデジタル情報に含まれた透かしとマグネチック線を用いて記録されたカードユーザ情報を含む。前記カード認証装置２００は、カード認証者がカードの認証だけでなく、個人身元情報やカードの内訳のような情報も共に確認できるようにデータベースと連動する構造にしてもよいが、カードの認証のみを行う装置の場合は、別途のカード情報データベースを含まない。
【００６１】
前記カード認証装置２００は、カードに含まれている情報を認識するためのカード認識部２１０と、ユーザキーを入力するためのキー入力部２２０と、カード認識部２１０から抽出されたデータを用いて該当ユーザのカードに対する情報を検索して抽出するデータベース検索情報抽出部２３０と、前記抽出された情報のうち、カード認証者が所望の情報を抽出するカード情報データベース部２４０と、カード認識部２１０から認識されるカードのデジタル画像の抽出等の処理ステップを行うデジタル画像データ処理部２５０と、抽出したデジタル画像とキー入力部２２０から入力されたユーザキーに基づいて生成する透かしを用いて認証を行う透かし認証サーバ２６０と、認証の結果を出力する結果出力部３００とを備えている。
【００６２】
以下、図６を参照して、このような構成を有するカード認証装置２００における各構成部材の動作と共に全体の動作ステップについて説明する。
【００６３】
カード認証者は、カードの偽変造の有無及びカード所持者の真偽を確認するために、カード所持者に、透かしが埋め込まれたカードの認証装置のカード認識部２１０にカードを入れてキー値をキー入力部２２０から入力させる（ステップＳ３００）。前記カード認識部２１０は、カード所持者が入れたカードからカードシリアルナンバーやカードユーザＩＤ等の読み取られた種々のカード情報をデータベース検索情報抽出部２３０に伝送する一方、カードに印刷されたイメージを走査し、カードに印刷されたイメージをデジタル画像データのフォーマットでデジタル画像データ処理部２５０に伝送する。
【００６４】
前記データベース検索情報抽出部２３０は、カード認識部２１０から伝送された種々のカード情報のうち、カード所持者の身元情報や取引きの内訳等、カード認証者が所望の情報を抽出するための検索情報（カードシリアルナンバーやユーザＩＤ等）を抽出して、カード情報データベース部２４０へ送る。検索情報の抽出は、カードに貼り付けられているマグネチック線とバーコードのように情報記録と表示の機能を行う要素に記録されている部分により行われる。前記カード情報データベース部２４０は、データベース検索情報抽出部２３０からの検索情報を用いてカード認証者が所望する所定のカードユーザに関する情報を抽出し、抽出した情報を結果出力部３００に伝送して、カードユーザ情報を得るステップを終了する（ステップＳ３４０〜Ｓ３６０）。
【００６５】
また、前記デジタル画像データ処理部２５０は、上述した透かしが埋め込まれたカードの製作時、透かしを埋め込んだデジタル画像領域に対応する領域内のイメージのみをキャプチャーして透かし認証サーバ２６０に伝送する。キャプチャーする領域内のイメージのサイズは、カードのサイズの範囲内であればよく、特に限定されるのではない。このとき、カード面に印刷されたイメージから透かしを検出するためには、透かしが埋め込まれた位置を知らなければならないので、透かしを埋め込むステップにおいて、透かしの埋込領域を予め決めておくと、透かし検出の際には、その領域に対応する位置のイメージのみを得ればよい。或いは、透かしを埋め込むとき、埋込領域を表示する別途の識別子を埋め込んだ場合は、該識別子を探索して探し出した後、該識別子により決められる領域内のイメージのみをキャプチャーする。透かし認証サーバ２６０に高速伝送するために、透かしが埋め込まれたイメージデータを圧縮してもよい。
【００６６】
前記透かし認証サーバ２６０は、キャプチャーしたイメージデータから透かしを検出する（ステップＳ３１０）。透かしの検出は、埋め込んだときに適用した透かし技法に対応する検出方法を用いる。検出した透かしとユーザキーにより生成する透かしを比較し（ステップＳ３２０）、比較結果による認証の結果をカード認証者が確認できる所定の形式に出力して、透かしの検出及び認証のステップを終了する（ステップＳ３３０）。このような機能を行う透かし認証サーバ２６０は、周波数領域への変換及び周波数領域係数を用いて透かしの検出を行う透かし検出部２７０と、ユーザが入力したキーを暗号化した後、暗号化されたキーを用いて透かしを生成する透かし生成部２９０と、透かし検出部２７０で検出した透かしと透かし生成部２９０で生成した透かしとの相関関係により認証の有無を決定する比較演算部２８０とを備えている。
【００６７】
以下、図７及び図８を参照して、透かしの検出方法について説明する。
前記透かし認証サーバ２６０の透かし検出部２７０は、デジタル画像データ処理部２５０からの透かし埋込みイメージを伝送され、本発明の検出方法に従い透かしを検出する。若し、デジタル画像データ処理部２５０においてイメージデータを圧縮した場合は、透かし検出部２７０は、これに対応してイメージデータの圧縮を解いた後に透かしを検出する。
【００６８】
また、カード所持者は、カード認証装置２００のキー入力部２２０にキー値を入力する。キー入力部２２０は、カード所持者から入力されたキー値をデジタル化したデータとして透かし認証サーバ２６０へ伝送する。透かし認証サーバ２６０の透かし生成部２９０は、透かし埋込時と同一の方法により、キー入力部２２０から伝送されたキーデータを暗号化し、暗号化したキーデータを用いて透かしを生成する。
【００６９】
次いで、比較演算部２８０は、透かし検出部２７０で検出した透かしと透かし生成部２９０で生成した透かしとの間の相関関係から認証の有無を決定し、その認証結果を結果出力部３００へ伝送する。
【００７０】
最後に、結果出力部３００は、カード情報データベース部２４０から抽出された、カード認証者が所望する所定の情報及び透かし認証サーバ２６０の比較演算部２８０から伝送された認証結果を、カード認証者が確認することができる形態に出力する。
【００７１】
前記ステップのうち、カード認識部２１０からカードが入れられたか否かが確認されると、カードの認証とカード所持者の真偽を判別するための透かし検出及び認証ステップ（ステップＳ３１０〜Ｓ３３０）と、カード認証者が必要とするカードユーザの情報をデータベースから検索して抽出するためのステップ（ステップＳ３４０〜Ｓ３６０）がそれぞれ行われる。二つのステップは互いに独立したプロセスであるため、二つのステップを平行して行うことが、処理時間を短縮することができるので好ましい。
【００７２】
以下、図７及び図８を参照して、本発明によるカード製作装置において用いられた透かし埋込方法と関連し、透かしを検出して認証するステップについて詳述する。
【００７３】
図７は、図５における透かし認証サーバの構成を具体的に示す詳細ブロック図であり、図８は、図７における構成によるカードの透かしの比較ステップを示すフローチャートである。
【００７４】
図７における透かし認証サーバを構成する各ブロックは、上述した透かし埋込部における構成部材と同一であるので、それぞれの機能についての説明は省略し、全体的な動作を記述する。
【００７５】
前記デジタル画像データ処理部２５０により処理された透かしが埋め込まれたデジタル画像が、白黒／カラー画像判別器４１０に入力される（ステップＳ４００）。この白黒／カラー画像判別器４１０は、透かしが埋め込まれたデジタル画像が白黒画像であるかカラー画像であるかを判別する（ステップＳ４１０）。透かしが埋め込まれたデジタル画像が白黒画像であると、周波数領域変換器４３０により輝度成分に対する周波数領域変換が行われ（ステップＳ４２０）、カラー画像であると、先にカラーモデル変換器４２０によりＨＳＢモード、ＹＩＱモードまたはＹＣｂＣｒモード等のカラーモデルに変換される（ステップＳ４３０）。周波数領域変換器４３０により輝度成分に対してＤＣＴ変換、ＤＷＴ変換、ＦＦＴ変換の周波数領域変換が行われる。
【００７６】
このようにして、透かしが埋め込まれたデジタル画像に対し、周波数領域変換後に得られる変換係数からデジタル画像に埋め込まれていた透かしを検出し、元の透かしを復元する（ステップＳ４５０）。透かしの検出は、所定の特定周波数領域の係数に特性関数を適用した結果に透かしを掛けて、他の所定の特定周波数領域の係数に埋め込むプロセスの逆プロセスを行うことであり、透かしが埋め込まれたデジタル画像から、上述した特定周波数領域に埋め込まれている代置係数（ＦＯＩ’）と、代置係数（ＦＯＩ’）の計算に用いられている埋込係数（ＦＯＩ）を求め、その埋込係数及び代置係数を用いて透かしを復元する。
【００７７】
また、透かし生成部２９０は、ユーザキーを入力され、ユーザキー暗号化器４４０により透かし埋込みステップと同様の方法で暗号化し、擬似乱数生成器４５０によりＰＮ-ｃｏｄｅ方式による透かし（Ｗ）を生成することになる。透かしの生成は、ユーザキーから透かしを生成する方法以外に、例えば、所定の保存媒体に予め保存されていた幾つかの透かしのうち、いずれか一つの透かしを埋込み及び検出する例もあり得る。このようにユーザキーが入力されていない場合は、埋込係数と代置係数から求めた透かしを、例えば予め保存されている幾つかの透かしと比較して、所定の透かしが埋め込まれているか否かを判断することができる。
このようにして、復元された透かし（ＷＥ）と、透かし埋込時に使用された方法により生成した透かし（Ｗ）との間の相関関係を分析することにより、デジタル画像に所定の透かしがあるか否かを検出することができる（ステップＳ４６０）。ところが、透かしが任意のサイズ値を有する順列である場合は、透かしを復元するために埋込係数と代置係数の値を使用しなければならず、例えば、透かしが１と−１のみを有する二進数列である場合は、特性関数ｆｘの値が常に正数であるとの仮定下で、代置係数の符号のみでも透かしの値を復元することができる。
【００７８】
前記比較演算部２８０で行われる相関関係の分析は、検出された透かし（ＷＥ）とユーザから入力されたキーを使用して生成した透かし（Ｗ）との相関関係及びその相関値を求め、ユーザが指定した透かしが埋め込まれたことを確認することにより、透かし認証装置２００で検査されるデジタル画像の真偽、変更の有無が分かる。
【００７９】
以下、透かし（ＷＥとＷ）間の相関関係及びその相関値を求める方法について説明する。透かし（ＷＥとＷ）間の相関関係は、下記の数９により求められる。
【００８０】
【数９】

【００８１】
ここで、
【００８２】
【数１０】

【００８３】
はＦＦＴ（Ｗ）の共役複素数を示し、ＩＦＦＴ（Ｗ）は逆ＦＦＴ（Ｗ）を示す。上記数９から求められた相関関係の結果は、ある一つの値でなく、シーケンスの形態Ｘ₁…Ｘ_Nであるので、求められた複数個の値Ｘ₁〜Ｘ_Nを比較して最大ピーク値Ｍ及びその位置Ｐを求める。その後、数９から求められた相関関係の結果から、尖度、即ち４次モーメント（Ｋｕｒｔｏｓｉｓ）Ｋを次の数１１によって求める。
【００８４】
【数１１】

【００８５】
ここで、Ｘ₁…Ｘ_Nは上述のように数９から得られる数列であって、透かし（ＷとＷＥ）間の相関関係の結果値であり、
【００８６】
【数１２】

【００８７】
はＸ₁…Ｘ_Nの平均を、σは標準偏差を示す。
【００８８】
このように求められた相関値Ｋ、Ｍ、Ｐを分析すると、所定のユーザキーで生成した透かし（Ｗ）と検出した透かし（ＷＥ）が一致するか否かを判別することができる。詳しく説明すると、相関値Ｋ、即ち尖度（Ｋｕｒｔｏｓｉｓ）が所定のしきい値未満であれば透かし（ＷとＷＥ）が一致しないことを示し、最大ピーク値Ｍが所定のしきい値未満である場合も、透かし（ＷとＷＥ）が一致しないことを示す。また、透かし（ＷとＷＥ）の最大ピーク値の位置Ｐが常に同一である場合にのみ透かし（ＷとＷＥ）が一致することを意味する。
【００８９】
また、透かし生成部で生成した擬似乱数は、自己の信号以外の擬似乱数とは相関度が‘０’であるので、擬似乱数による相関度もまた、所定のしきい値以上である場合は、透かし（ＷとＷＥ）が一致することを意味する。従って、デジタル画像が上述した相関値の条件を全て満たしていると、透かし（ＷとＷＥ）が一致することを意味するので、デジタル画像の認証を確定することができることになる。
【００９０】
産業上の利用可能性
以上のように、本発明によると、クレジットカード、ＩＣカード、スマートカード、学生証、社員証、カードキーのようなカードに加えられ得る不法行為を防止すると共に、このようなカードが偽変造された場合を容易に検出することができ、カードとカード所持者の真偽を確認／決定する認証効果を得ることができる。特に、データベースシステムと連動すれば、カードの真偽の認証以外にも身元情報を同時に把握することができる。また、磁性体との接触等に影響されず、取扱性も良好である。
【００９１】
以上、本発明による透かしが埋め込まれたカードの製作方法及び認証方法、並びにそれらの装置についてその好ましい実施の形態を開示してこれを例示により説明したが、これは、この技術の分野における熟練者にとって、このような実施の形態は単に例示のためのものであって、これに限定されるものではなく、本発明の技術的思想の範囲内で種々に変更または変形され、置き換えられることは明白である。
また、本発明の技術的思想は、上述した実施の形態に限定されず、添付の特許請求の範囲及びそれと同等の技術的原理によってのみ限定されるものである。
【図面の簡単な説明】
【図１】 本発明による一実施の形態の電子透かしが埋め込まれたカードの製作装置の概略構成を示すブロック図である。
【図２】 図１におけるカード製作装置による透かしが埋め込まれたカードの製作ステップを説明するフローチャートである。
【図３】 図１における透かし関連構成を具体的に示す詳細ブロック図である。
【図４】 図３における構成により透かしが埋め込まれたデジタル画像の製作ステップを示すフローチャートである。
【図５】 図１におけるカード製作装置により製作されたカードを認証するためのカード認証装置の構成を示すブロック図である。
【図６】 図５におけるカード認証装置でのカード認証ステップを示すフローチャートである。
【図７】 図５における透かし認証サーバの構成を具体的に示す詳細ブロック図である。
【図８】 図７における構成によるカードの透かしの比較ステップを示すフローチャートである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for producing a card on which digital information is printed using digital watermark technology, and more specifically to an apparatus for the same. It is related with the manufacturing method and authentication method of the card | curd with which the digital information formed by embedding the watermark which cannot be identified with the naked eye and was printed, and those apparatuses.
[0002]
[Prior art]
Conventionally, in order to verify identity and qualification, ID card such as resident registration card, passport, student ID card, employee ID card, or identification information like driver's license, certificate, credit card, card key, etc. In addition, various cards for verifying / verifying the identity are widely used. However, in spite of the importance of the information contained in such cards, the actual situation is that cases where cards are illegally falsified and altered and used are increasing.
[0003]
In order to solve such problems, the following methods have been proposed and used.
[0004]
First, there is a method in which a photograph is pasted on a printing paper on which identification information or the like is printed. This is currently used in passports and the like. However, this method simply authenticates both the card and the holder if the card photo and its holder match, so after removing the coated paper and replacing the photo, There was a problem that it could be changed easily.
Secondly, there is a barcode method which is a coding system that expresses information with an arrangement pattern of black bars and white bars having various widths. If an identification card is produced by pasting or printing a barcode, it is possible to confirm the authenticity of the identification card, the identity information, and the authenticity of the holder based on the information read from the barcode reader at the time of entry / exit. However, since barcodes are easy to duplicate, the same pattern barcodes can be imitated and used illegally, and even if this pattern is changed, it becomes a completely different authentication document. There is a lot of room to be done. Moreover, it is often impossible to read a bar code with a bar code reader, and a keyboard must be provided for this purpose.
[0005]
Third, there is a magnetic line on which certain information is magnetically recorded, but most credit cards attach a magnetic line to the back of the card and record the information on this magnetic line. The method that provides the minimum information for is adopted.
[0006]
[Problems to be solved by the invention]
However, in the case of such a method, touching an object with strong magnetism easily damages information recorded on the magnetic line, and it is easy to read the information recorded on the magnetic line. There is a problem with it.
[0007]
Furthermore, there are two main methods for determining the authenticity of the cardholder, one of which is to make a visual decision with a photograph, and the other is to make a determination using a personal identification number. It is. However, the method using a photo is not meaningful as a discrimination method in the situation where forgery and alteration are easy as described above, and it is also possible to discriminate by comparing the card holder and the photo affixed or printed on the card one by one. Has to be inferior in discrimination power due to time constraints.
[0008]
The method of contrasting the cardholder's PIN with the actual PIN is currently the most widely used discriminating method, but since the PIN generally consists of four-digit Arabic numerals, it is obvious to those who have illegal intentions. Cheap. Although the security code can be updated frequently to maintain security from a third party, it has the disadvantage that it is very complicated to go through the renewal procedure again or to create and store a new security code . Of course, both the naked eye discrimination method using a photograph and the PIN code contrast method can be used, but even if the two methods are used in parallel, the above-mentioned problems cannot be solved clearly.
[0009]
Of course, recently, in order to solve such a problem, a method of digitizing and printing information recorded on a card may be adopted. However, such digitalization allows unlimited copying without damaging the original, and it is difficult to distinguish the original from the original, so illegal copying and illegal distribution are performed indiscriminately. It is the actual situation.
[0010]
These methods are currently applied to prevent illegal use due to forgery and alteration of cards, etc., but can be identified with the naked eye, the recorded information can be easily read and changed, and can be concealed. There were various problems, such as the amount of information being extremely weak, easily damaged, and time-constrained. Due to these limitations of the prior art, there is a risk of illegal use of cards, despite their importance.
[0011]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and digital information is printed using a digital watermark technology that prevents a card from being falsified by embedding a watermark that cannot be identified with the naked eye in a printed digital image. It is an object of the present invention to provide a manufactured card, its production, authentication method and apparatus.
[0012]
It is another object of the present invention to provide a card that can be printed with a watermark embedded while minimizing the deterioration of the quality of digital information printed on the card, and a method for manufacturing and authenticating the card.
[0013]
Furthermore, the present invention embeds a watermark in digital information to be printed using frequency domain characteristics, so that the quality of the digital information is not deteriorated, and the preservation property of the watermark against the deformation of the image printed on the card is improved. It is still another object of the present invention to provide a card on which digital information having high and strong characteristics is printed, its manufacture, and an authentication method and apparatus.
[0014]
In order to achieve the above object, an apparatus for producing a card in which information for authentication according to the present invention is embedded comprises means for storing card issuing information and card authentication information of a card issuing applicant, and the storing means Means for converting the card issuing information into a digital image having a shape of a predetermined size, means for setting the card authentication information of the storage means with a user key, and generating a watermark using the user key; Means for embedding the watermark in a digital image, and means for printing the digital image in which the watermark is embedded on the raw material of the card.
[0015]
According to the present invention, there is provided an authentication device for a card in which information for authentication is embedded, means for generating a digital image by scanning an image printed on the card, and inputting card authentication information from the card holder. Means for calculating the correlation between the watermark generated using the card authentication information input from the card holder and the watermark detected from the digital image, and determining the presence or absence of authentication; It is characterized by providing.
[0016]
The method performed by such an apparatus can also be configured in the same form.
Thus, when the card is manufactured, it is possible to prevent the card from being changed by embedding a watermark that cannot be identified with the naked eye. In addition, when the key determined by the true cardholder is generated as a watermark, the watermark detected from the card and the key entered by the cardholder at the time of authentication of the card or determination of authenticity of the cardholder It is possible to determine whether the card has been changed, whether or not the card has been made, and whether the card holder is true or false depending on whether or not they match. Moreover, the contents of the information that can be concealed can be varied, and the position where the information can be concealed can be arbitrarily selected. In addition, the watermark itself is not at risk of being damaged, and is difficult to change. Furthermore, an accurate and quick inspection can be performed by detecting and comparing watermarks using a computer.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, a general card issuing process will be described. The card issuer provides the card producer / issuer with information necessary for issuing the card, such as identity information (for example, name, resident registration number, address, bank account number, etc.) and photo. At this time, the card issuer determines a key value and provides it to the card producer / issuer. This key is character or numeric information such as a personal identification number, employee number, or various IDs. The card producer / issuer stores the information provided by the card issuance applicant including the key in the database, and extracts only the information printed on the card raw material from the database out of the information from the card issuance applicant. . Then, using a general card production graphic tool, a digital image including information to be printed on the card raw material extracted from the database is produced. By printing a digital image produced using a general card production printer on the raw material of the card, the card production is completed and issued to the card issuer.
[0018]
In the present invention, the above-described card production step further includes a step of embedding a watermark in a digital image printed on the raw material of the card after generating the watermark using the key provided by the card issuer, thereby The key can be concealed to make it difficult to imitate or duplicate, and the card can be prevented from being counterfeited. Further, by detecting a concealed key and determining whether or not the card holder matches the key input from the external input device, the card can be authenticated or the authenticity of the card holder can be determined. .
[0019]
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a schematic configuration of a card manufacturing apparatus in which an electronic watermark is embedded according to an embodiment of the present invention. As shown in FIG. 1, the card production apparatus 10 includes a card information database 20 including information necessary for card issuance, a digital image generation unit 30 that implements a digital image using the card information, and a user key value. A watermark generation unit 40 that generates a watermark, a watermark embedding unit 50 that embeds the generated watermark in a digital image, and a digital image printing unit 60 that prints the digital image embedded with the watermark on a card are provided.
[0020]
Next, with reference to FIG. 2, a description will be given of steps for producing a card with a watermark embedded by the card production apparatus.
[0021]
The card information database 20 stores information and key values necessary for the card issuer's card issuance and data related to the use of various cards. The key value and the information printed on the card are extracted (step S100). The data extracted in this way uses a card production graphic tool to produce a basic digital image to be printed on the card raw material based on the information extracted from the card information database 20. In the graphic tool, a predetermined area is set in consideration of the size of a card to be printed, and then various materials are written at preset positions to create one data file (step S110).
[0022]
In addition, the watermark generating unit 40 generates a watermark using the user key extracted from the card information database 20 (step S120). The generated watermark is embedded in the digital image (step S130). The watermark generated by the watermark generation unit 40 is embedded in the digital image by the watermark embedding unit 50 (step S130). Finally, by printing the digital image with the watermark embedded on the raw material of the card, the production of the card with the watermark embedded is completed (step S140). In particular, in the present invention, a method different from the conventional method is newly applied to generate and embed a watermark to be embedded in a card, which will be described with reference to FIGS.
[0023]
FIG. 3 is a detailed block diagram specifically showing the watermark-related configuration in FIG. 1, and FIG. 4 is a flowchart showing the steps for producing a digital image in which the watermark is embedded by the configuration in FIG.
[0024]
FIG. 3 shows the detailed configuration of the watermark generation unit 40 and the watermark embedding unit 50. The watermark generation unit 40 encrypts a user key input from the card information database 20. 41 and a pseudo random number generator 42 for generating a pseudo random number from the encrypted user key. In addition, the watermark embedding unit 50 includes a monochrome / color image discriminator 100 that discriminates whether an input digital image is monochrome or color, and processes an image when the input image is color. A color model converter 110 for converting a color model for easy execution, a frequency domain converter 120 for converting an input signal from a spatial domain to a frequency domain, and a watermark generated by the watermark generation unit 40 in the frequency domain. A watermark embedder 130 for embedding in the transformed digital image, an inverse frequency domain transformer 140 for transforming the digital image with the watermark embedded from the frequency domain to the spatial domain, and the transformed signal as a color model. In some cases, an inverse color model converter 150 is provided for conversion to the original color model.
[0025]
Next, operations in the watermark generation unit 40 and the watermark embedding unit 50 having such a configuration will be described with reference to FIG.
[0026]
The digital image generated by the digital image generation unit 30 is input to the watermark embedding unit 50 (step S200). The input digital image is input to the monochrome image / color image discriminator 100, and it is determined whether the digital image in which the watermark is embedded is a monochrome image or a color image (step S210). The monochrome image / color image discriminator 100 extracts image information data relating to the format of the input digital image, and discriminates whether the image is a monochrome image or a color image from the extracted image information data.
[0027]
If the black and white image / color image discriminator 100 determines that the digital image is black and white, the frequency domain converter 120 converts the digital image into a frequency domain (step S220). ₁ ). At this time, since the black and white image has only a luminance component, the frequency domain converter 120 immediately converts from the spatial domain to the frequency domain.
[0028]
On the other hand, if the result of discrimination by the monochrome / color image discriminator 100 is a color image, first, in the color model converter 110, for example, from the RGB mode color model, HSB (H: hue, S: saturation, B: brightness). ) Mode, YIQ (Y: luminance, I: in-phase, Q: quadrature) mode or YCbCr (Y: luminance, Cb / Cr: chrominance) mode color model, and the luminance component of the converted color model is Extracted (step S215). The luminance component of the color model converted by the color model converter 110 is converted into the frequency domain by the frequency domain converter 120 (step S220). ₂ ). There are various techniques for transforming a digital image into the frequency domain. Typically, FFT transform (Fast Fourier Transform), DCT transform (Discrete Cosine Transform), DWT transform (Discrete Wavelet Transform), and the like are used.
[0029]
In the present invention, the frequency domain method is used for embedding and detecting the watermark. This is because the conversion by the frequency domain method conceals the watermark in the digital image by converting the digital image into the frequency domain. This is because it is difficult to remove the watermark and does not significantly reduce the quality of the original digital image. According to the frequency domain converter 120, the DCT coefficient, FFT coefficient, or DWT coefficient (FOI) of the digital image is obtained.
[0030]
However, in the Fourier transform, since the coefficients in the transform domain are composed of complex numbers, it is difficult to embed watermark information in the Fourier transform coefficients. On the other hand, the DCT transform has characteristics similar to the Fourier transform. Since the coefficients of the region are composed only of real numbers, it is more advantageous and easier than the Fourier transform. Here, an embodiment in which a watermark is embedded in a DCT transform coefficient or DWT transform coefficient relating to a digital image will be described. DCT conversion is basically closely related to FFT conversion, and is a conversion technique widely used in standard JPEG compression and the like. The one-dimensional DCT transform is defined as the following formula 1.
[0031]
[Expression 1]

[0032]
In Equation 1, s is the original signal value, t is the converted signal value, N indicates the length of the signal, and coefficient c is defined as in Equation 2 below.
[0033]
[Expression 2]

[0034]
(However, 1 ≦ k ≦ N−1).
Further, the two-dimensional DCT transform for the square matrix is defined as the following Equation 3.
[0035]
[Equation 3]

[0036]
In Equation 3, N, s, and t have the same meaning as in the one-dimensional DCT transform, and c (i, j) is defined as Equation 4 below.
[0037]
[Expression 4]

[0038]
(However, this is the case when i ≠ 0 and j ≠ 0).
Further, the DCT transform has an inverse transform and is defined as the following formulas 5 and 6 for one dimension and two dimensions, respectively.
[0039]
[Equation 5]

[0040]
[Formula 6]

[0041]
Next, DWT conversion will be described. If the Fourier transform is a transform that uses a sine function and a cosine function as basis functions, the wavelet transform is a transform that uses a wavelet as a basis function, and is roughly divided into a continuous wavelet transform and a discrete wavelet transform. The continuous wavelet transform is expressed as the following Expression 7.
[Expression 7]

[0042]
In Equation 7, s represents scaling, τ represents translation, and ψ (s, t) represents a scaled and moved wavelet.
[0043]
Scaling is related to frequency, with low scaling, ie, compressed wavelets, extracting high frequency components and high scaling, ie, expanded wavelets, extracting low frequency components. Usually, the continuous wavelet transform cannot be actually implemented because the wavelet coefficients obtained by the transformation can be obtained infinitely as a function of scaling and position movement.
[0044]
Therefore, the discrete wavelet transform that selects only a certain frequency region for scaling and position movement can be implemented more effectively. However, since the discrete wavelet transform is also burdened by a large amount of calculation to be implemented by a computer, it is preferable to convert an image image using a filter bank which is a high-speed wavelet transform. This method can be easily implemented as long as the relationship between filter banks for inverse transformation (PR-QMF) is established, using classical two-channel subband coding and a pyramid algorithm. There is an advantage that you can.
[0045]
The watermark generation unit 40 receives a predetermined user key from the card information database 20 and generates a watermark from the user key. When the user key is used as a watermark, the authenticity of the digital image and whether or not it has been changed can be determined more accurately based on the correlation between the detected watermark and the watermark generated from the user key. There is an advantage of strengthening.
[0046]
In addition, before generating a pseudo random number used as a watermark from the user key, the user encrypts the user key using the encryptor 41, and then the encrypted key is input. The pseudo random number generator 42 Generate pseudo-random numbers. When the user key undergoes the encryption step, the user key value is not easily deformed, but the user key itself can be concealed. Therefore, when the watermark generated from the encrypted user key is embedded in the digital image, There is an advantage that the user key itself is not disclosed when a watermark is detected from a digital image. For the encryption, a normal encryption method such as a DES (data encryption standard) method, an RSA method, an ECC method, or the like can be used. In the present invention, a PN-code method is used, in which data to be encrypted is coded and the result is output as a pseudo random number.
[0047]
When the watermark is generated in this way, the watermark embedder 130 embeds it in the digital image through the process of the following mathematical formula 5 (step S230). ₁ Or S230 ₂ ).
[0048]
[Equation 8]

[0049]
Here, fx is a characteristic function for adjusting the strength of the watermark embedded in the digital image. fx can be set in various ways. A part of the frequency domain transform coefficient (FOI) of the digital image is modulo-modulated, or a statistical characteristic value such as an average, standard deviation, and variance of a large number of transform coefficients is obtained. It may be a function to be extracted.
[0050]
FOI ′ indicates a result of applying a watermark (W) to a value obtained by applying the characteristic function fx to the frequency domain transform coefficient (FOI) of the digital image. Since the transform coefficient (FOI) in Equation 5 is a value in the frequency domain of the digital image, it is in the form of a two-dimensional array, and the watermark (W) has the form of a one-dimensional permutation (sequence). FOI) is in the form of a permutation, or watermark (W) is converted into a two-dimensional block. For calculation, one watermark can be calculated for each frequency coefficient of an image, and there is a method of obtaining a statistical characteristic of frequency coefficients of a plurality of images and calculating with one watermark.
[0051]
Next, the step of embedding a watermark will be described in detail with reference to Equation 8.
The watermark embedder 130 multiplies the value obtained by applying the characteristic function fx to the absolute value of a transform coefficient (hereinafter referred to as an embedding coefficient) in a predetermined specific frequency region and the result (FOI ′, A process of replacing a substitution coefficient) with a conversion coefficient in another predetermined specific frequency region is performed. For example, when a digital image is divided into low-frequency, intermediate-frequency, and high-frequency regions, watermarks are embedded in the intermediate-frequency region or high-frequency region that contains relatively little digital image information. A watermark is obtained by substituting the transformation coefficient of the existing intermediate frequency region and high frequency region with the result (substitution factor) obtained by multiplying the value obtained by applying the characteristic function fx to the transformation factor (embedding factor) of the region. The embedding is completed.
[0052]
According to such a method, even if there is a compression step or a blurring that discards a part of the high frequency portion, the watermark is multiplied by a coefficient in the low frequency region and replaced in the high frequency region. As a result, a considerable portion of the high-frequency region remains after deformation, which has the advantage of being resistant to deformation.
[0053]
In the present specification, the watermark is multiplied by the result of applying the characteristic function fx to the absolute value of the coefficient in the low frequency region, and is substituted between the intermediate frequency region and the high frequency region as an example. Alternatively, a watermark may be embedded by selecting a frequency region that does not degrade the quality of the digital image. For example, after applying the watermark to the result of applying the characteristic function to the absolute value of the transform coefficient in the high frequency domain, it can be replaced in the high frequency domain, so the method of embedding the watermark in the digital image converted to the frequency domain is The present invention is not limited to this and can be applied in various frequency regions.
[0054]
In addition, the present invention pays attention to the fact that the overall characteristics of the image do not change so much by printing, and changes to the overall characteristics of the image by compensating the coefficients of other frequency domains with the coefficients of an arbitrary frequency domain. If the characteristics in the frequency domain that do not give the image are used, it has a strong characteristic in printing, so that it is possible to prevent the watermark from being erased by printing or the like. Further, according to the watermark embedding method using the characteristics of the frequency domain described above, even if the watermark is embedded, the overall characteristics of the digital image are not changed, that is, the quality of the original digital image is not deteriorated. Appreciate the quality of the original digital image.
[0055]
In Equation 8, when the watermark is embedded in the digital image, it is the fx function that adjusts the strength of the watermark. Since this characteristic function value can be arbitrarily set by the user, any value is possible. In particular, the characteristic function value can be determined by an appropriate function so as not to deteriorate the quality of the digital image due to embedding of the watermark (W). . That is, since the strength of the watermark and the deformation of the quality of the digital image are inversely proportional to each other, it is preferable to determine in consideration of the use environment of the watermark and the aspect of maintaining the quality of the digital image.
[0056]
Next, in order to obtain the digital image in which the watermark is embedded, the inverse frequency domain converter 140 restores the digital image converted into the frequency domain (step S240). ₁ Or S240 ₂ ). When the frequency domain converter 120 uses DCT, DWT, or FFT, the inverse frequency domain 140 uses inverse DCT, inverse DWT, or inverse FFT. Here, when the digital image is a color image, the inverse color model converter 150 calculates the remaining components excluding the luminance component that has been subjected to the inverse frequency domain conversion and the luminance component that has not been subjected to the frequency domain conversion. The color model of the HSB mode, YIQ mode or YCbCr mode is restored to the original color model (step S245). Finally, by obtaining a digital image in which the watermark is embedded, the process of embedding the watermark in the digital image ends (step S250).
[0057]
In this manner, when the watermark embedding step for the digital image is completed, a card in which the watermark is embedded by printing on the card surface from the digital image printing unit 60 on the card surface can be manufactured.
[0058]
In the card in which the watermark according to the present invention is embedded as described above, the embedded watermark can be variously determined according to the position and contents. Whether the content of the watermark is letters, numbers, or an image, or whether the watermark is embedded in the whole or a part of the card can be determined in various ways depending on the characteristics of the watermark technique selected by the card producer / issuer. For example, in the above-described step of producing a card with a watermark embedded, if the portion where the watermark is embedded is a photo of the card issuer, first, a predetermined space in which the photo is printed is left blank, and the card is left on the card in addition to the photo. After printing only the information to be printed on the card's raw materials, the card issuer's photo is produced as a digital image, and after embedding the watermark only in this digital image, the digital image with the watermark embedded is printed on the card. You may print in the predetermined position of raw materials. On the other hand, if the part where the watermark is to be embedded is the entire card, after the information printed on the card is produced into a digital image of the same size as the entire raw material of the card, the watermark is embedded in this digital image You may print on the raw material of the card. Alternatively, when the watermark is embedded in a specific part of the image printed on the card, a method of displaying a specific identifier in the part where the watermark is embedded may be used.
[0059]
Hereinafter, an apparatus and a method for authenticating a card in which a watermark created through such a production step is embedded will be described with reference to FIGS. The step and apparatus for authenticating the card with embedded watermark is configured to correspond to the above-described card production step and apparatus, and the watermark detection technique used in the step of authenticating the card with embedded watermark is: This corresponds to the watermark embedding technique used in the step of producing a card with embedded watermark.
[0060]
FIG. 5 is a block diagram showing a configuration of a card authentication apparatus for authenticating a card manufactured by the card manufacturing apparatus in FIG. The card authentication apparatus 200 in FIG. 5 is roughly divided into a part for generating a watermark by inputting a user key and a part for processing information recorded on the card itself. The information recorded on the card itself includes card user information recorded using a watermark and a magnetic line included in digital information printed on the surface of the card. The card authenticating apparatus 200 may be structured in conjunction with a database so that the card authenticator can check not only the card authentication but also the personal identification information and the breakdown of the card, but only the card authentication. In the case of a device that performs this, a separate card information database is not included.
[0061]
The card authentication apparatus 200 uses a card recognition unit 210 for recognizing information included in the card, a key input unit 220 for inputting a user key, and data extracted from the card recognition unit 210. From the database search information extraction unit 230 that searches and extracts information on the card of the corresponding user, the card information database unit 240 from which the card authenticator extracts desired information among the extracted information, and the card recognition unit 210 Authentication is performed using a digital image data processing unit 250 that performs processing steps such as extraction of a digital image of a recognized card, and a watermark generated based on the extracted digital image and a user key input from the key input unit 220. The watermark authentication server 260 and a result output unit 300 that outputs the authentication result are provided.
[0062]
Hereinafter, with reference to FIG. 6, the overall operation steps as well as the operation of each component in the card authentication apparatus 200 having such a configuration will be described.
[0063]
The card authenticator inserts the card into the card recognition unit 210 of the authentication device of the card in which the watermark is embedded in order to confirm whether the card is falsified or not and whether the card holder is authentic or not. Is input from the key input unit 220 (step S300). The card recognition unit 210 transmits various pieces of card information read from the card inserted by the cardholder, such as a card serial number and a card user ID, to the database search information extraction unit 230, while an image printed on the card is transmitted. The image scanned and printed on the card is transmitted to the digital image data processing unit 250 in the format of digital image data.
[0064]
The database search information extraction unit 230 is a search for extracting information desired by the card authenticator, such as the identity information of the card holder and the breakdown of transactions, among the various pieces of card information transmitted from the card recognition unit 210. Information (card serial number, user ID, etc.) is extracted and sent to the card information database unit 240. Extraction of search information is performed by a portion recorded in an element that performs information recording and display functions such as a magnetic line and a bar code pasted on a card. The card information database unit 240 extracts information about a predetermined card user desired by the card authenticator using the search information from the database search information extraction unit 230, and transmits the extracted information to the result output unit 300. The step of obtaining card user information is terminated (steps S340 to S360).
[0065]
Further, the digital image data processing unit 250 captures only the image in the area corresponding to the digital image area in which the watermark is embedded and transmits the image to the watermark authentication server 260 when the card in which the watermark is embedded is manufactured. The size of the image in the area to be captured is not particularly limited as long as it is within the size range of the card. At this time, in order to detect the watermark from the image printed on the card surface, it is necessary to know the position where the watermark is embedded, so in the step of embedding the watermark, if the watermark embedding area is determined in advance, When detecting a watermark, it is only necessary to obtain an image at a position corresponding to the area. Alternatively, when embedding a watermark, if a separate identifier for displaying the embedding area is embedded, after searching for and searching for the identifier, only the image in the area determined by the identifier is captured. The image data in which the watermark is embedded may be compressed for high-speed transmission to the watermark authentication server 260.
[0066]
The watermark authentication server 260 detects a watermark from the captured image data (step S310). The detection of the watermark uses a detection method corresponding to the watermark technique applied when embedding. The detected watermark is compared with the watermark generated by the user key (step S320), the authentication result based on the comparison result is output in a predetermined format that can be confirmed by the card authenticator, and the watermark detection and authentication steps are completed (step S320). Step S330). The watermark authentication server 260 performing such a function includes a watermark detection unit 270 that performs conversion to a frequency domain and detects a watermark using a frequency domain coefficient, and encrypts a key input by a user and then encrypts the key. A watermark generation unit 290 that generates a watermark using a key, and a comparison operation unit 280 that determines the presence or absence of authentication based on the correlation between the watermark detected by the watermark detection unit 270 and the watermark generated by the watermark generation unit 290 are provided. Yes.
[0067]
Hereinafter, a watermark detection method will be described with reference to FIGS.
The watermark detection unit 270 of the watermark authentication server 260 receives the watermark embedded image from the digital image data processing unit 250 and detects a watermark according to the detection method of the present invention. If the digital image data processing unit 250 compresses the image data, the watermark detection unit 270 detects the watermark after decompressing the corresponding image data.
[0068]
Further, the card holder inputs a key value to the key input unit 220 of the card authentication device 200. The key input unit 220 transmits the key value input from the card holder to the watermark authentication server 260 as digitized data. The watermark generation unit 290 of the watermark authentication server 260 encrypts the key data transmitted from the key input unit 220 by the same method as when embedding the watermark, and generates a watermark using the encrypted key data.
[0069]
Next, the comparison operation unit 280 determines the presence / absence of authentication from the correlation between the watermark detected by the watermark detection unit 270 and the watermark generated by the watermark generation unit 290, and transmits the authentication result to the result output unit 300. .
[0070]
Finally, the result output unit 300 displays the predetermined information desired by the card authenticator extracted from the card information database unit 240 and the authentication result transmitted from the comparison operation unit 280 of the watermark authentication server 260 by the card authenticator. Output to a form that can be confirmed.
[0071]
Of the above steps, when it is confirmed whether or not a card has been inserted from the card recognition unit 210, a watermark detection and authentication step (steps S310 to S330) for determining authentication of the card and authenticity of the cardholder, Steps (steps S340 to S360) for searching and extracting information on card users required by the card authenticator from the database are performed. Since the two steps are independent processes, it is preferable to perform the two steps in parallel because the processing time can be shortened.
[0072]
Hereinafter, a step of detecting and authenticating a watermark will be described in detail with reference to FIGS. 7 and 8 in connection with the watermark embedding method used in the card manufacturing apparatus according to the present invention.
[0073]
FIG. 7 is a detailed block diagram specifically showing the configuration of the watermark authentication server in FIG. 5, and FIG. 8 is a flowchart showing the card watermark comparison step according to the configuration in FIG.
[0074]
Each block constituting the watermark authentication server in FIG. 7 is the same as the constituent members in the watermark embedding unit described above, and therefore description of each function is omitted and the overall operation is described.
[0075]
The digital image embedded with the watermark processed by the digital image data processing unit 250 is input to the monochrome / color image discriminator 410 (step S400). The monochrome / color image discriminator 410 discriminates whether the digital image in which the watermark is embedded is a monochrome image or a color image (step S410). If the digital image in which the watermark is embedded is a monochrome image, the frequency domain converter 430 performs frequency domain conversion on the luminance component (step S420). If the digital image is a color image, the color model converter 420 first performs HSB mode. The color model is converted into a color model such as YIQ mode or YCbCr mode (step S430). The frequency domain converter 430 performs frequency domain conversion of DCT conversion, DWT conversion, and FFT conversion on the luminance component.
[0076]
In this way, the watermark embedded in the digital image is detected from the conversion coefficient obtained after the frequency domain conversion for the digital image in which the watermark is embedded, and the original watermark is restored (step S450). The detection of a watermark is a process in which a watermark is applied to the result of applying a characteristic function to a coefficient in a predetermined specific frequency domain and the process of embedding in a coefficient in another predetermined specific frequency domain is performed, and the watermark is embedded. From the digital image, the substitution coefficient (FOI ′) embedded in the specific frequency region and the embedding coefficient (FOI) used for calculation of the substitution coefficient (FOI ′) are obtained, and the embedding is performed. The watermark is restored using the coefficients and substitution coefficients.
[0077]
Also, the watermark generation unit 290 receives the user key, encrypts it by the user key encryptor 440 in the same manner as the watermark embedding step, and generates a watermark (W) by the PN-code method by the pseudo random number generator 450. It will be. In addition to the method of generating a watermark from a user key, for example, there is an example in which any one of several watermarks stored in advance in a predetermined storage medium is embedded and detected. When the user key is not input in this way, the watermark obtained from the embedding coefficient and the substitution coefficient is compared with, for example, several watermarks stored in advance, and whether or not a predetermined watermark is embedded. Can be determined.
In this way, by analyzing the correlation between the restored watermark (WE) and the watermark (W) generated by the method used at the time of watermark embedding, the digital image has a predetermined watermark. Whether or not can be detected (step S460). However, if the watermark is a permutation with an arbitrary size value, then the embedding coefficient and substitution coefficient values must be used to recover the watermark, for example, the watermark has only 1 and -1. In the case of a binary number sequence, the watermark value can be restored using only the sign of the substitution coefficient under the assumption that the value of the characteristic function fx is always a positive number.
[0078]
The correlation analysis performed by the comparison calculation unit 280 is performed by obtaining a correlation between the detected watermark (WE) and a watermark (W) generated using a key input from the user and a correlation value thereof, By confirming that the watermark designated by is embedded, it is possible to know whether the digital image inspected by the watermark authenticating apparatus 200 is authentic or not.
[0079]
Hereinafter, a correlation between watermarks (WE and W) and a method for obtaining the correlation value will be described. The correlation between the watermarks (WE and W) is obtained by the following equation (9).
[0080]
[Equation 9]

[0081]
here,
[0082]
[Expression 10]

[0083]
Indicates a conjugate complex number of FFT (W), and IFFT (W) indicates inverse FFT (W). The result of the correlation obtained from the above equation 9 is not a single value, but a sequence form X ₁ ... X _N Therefore, a plurality of calculated values X ₁ ~ X _N Are obtained to obtain the maximum peak value M and its position P. Thereafter, kurtosis, that is, a fourth-order moment (Kurtosis) K is obtained by the following equation 11 from the result of the correlation obtained from equation 9.
[0084]
[Expression 11]

[0085]
Where X ₁ ... X _N Is a sequence obtained from Equation 9 as described above, and is a result value of the correlation between watermarks (W and WE),
[0086]
[Expression 12]

[0087]
Is X ₁ ... X _N Where σ is the standard deviation.
[0088]
By analyzing the correlation values K, M, and P thus obtained, it is possible to determine whether or not the watermark (W) generated with a predetermined user key matches the detected watermark (WE). More specifically, if the correlation value K, that is, kurtosis, is less than a predetermined threshold, it indicates that the watermarks (W and WE) do not match, and the maximum peak value M is less than the predetermined threshold. This also indicates that the watermarks (W and WE) do not match. It also means that the watermarks (W and WE) match only when the maximum peak value position P of the watermarks (W and WE) is always the same.
[0089]
Further, since the pseudo random number generated by the watermark generation unit has a correlation degree of '0' with a pseudo random number other than its own signal, if the correlation degree by the pseudo random number is also equal to or greater than a predetermined threshold value, This means that the watermarks (W and WE) match. Therefore, if the digital image satisfies all the above-described correlation value conditions, it means that the watermarks (W and WE) match, so that authentication of the digital image can be confirmed.
[0090]
Industrial applicability
As described above, according to the present invention, illegal activities that can be applied to a card such as a credit card, an IC card, a smart card, a student ID card, an employee ID card, and a card key are prevented, and such a card is counterfeited. Can be easily detected, and an authentication effect for confirming / determining the authenticity of the card and the cardholder can be obtained. In particular, when linked with a database system, it is possible to simultaneously grasp identity information other than authentic authentication of a card. Moreover, it is not affected by the contact with the magnetic material and the handling property is also good.
[0091]
As described above, the preferred embodiment of the manufacturing method and the authentication method of the card in which the watermark is embedded according to the present invention and the apparatuses thereof have been disclosed and described by way of example. Therefore, such embodiments are merely illustrative, and are not limited thereto, and it is obvious that various changes, modifications, and substitutions may be made within the scope of the technical idea of the present invention. It is.
Further, the technical idea of the present invention is not limited to the above-described embodiment, but is limited only by the appended claims and the technical principle equivalent thereto.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a card manufacturing apparatus in which a digital watermark is embedded according to an embodiment of the present invention;
FIG. 2 is a flowchart for explaining steps of producing a card with a watermark embedded therein by the card production apparatus in FIG. 1;
FIG. 3 is a detailed block diagram specifically showing a watermark-related configuration in FIG. 1;
4 is a flowchart showing steps for producing a digital image in which a watermark is embedded according to the configuration shown in FIG. 3;
FIG. 5 is a block diagram showing a configuration of a card authentication device for authenticating a card manufactured by the card manufacturing device in FIG. 1;
6 is a flowchart showing a card authentication step in the card authentication apparatus in FIG. 5. FIG.
7 is a detailed block diagram specifically showing the configuration of the watermark authentication server in FIG. 5. FIG.
FIG. 8 is a flowchart showing a card watermark comparison step according to the configuration of FIG. 7;

Claims (17)

In a card production device in which information for authentication is embedded,
Means for storing the card issuer's card issue information and card authentication information;
Means for converting the card issuing information of the storage means into a digital image having a shape of a predetermined size;
Means for setting the card authentication information of the storage means with a user key, and generating a watermark using the user key;
Means for embedding the watermark in the digital image;
Means for printing the watermarked digital image on the card stock,
Means for embedding the watermark;
A frequency domain conversion means for converting the luminance component of the digital image into a frequency domain coefficient divided into two or more areas having at least a first frequency area and a second frequency area;
Of the frequency domain coefficients, the substitution coefficient generated using the first frequency domain coefficient and the watermark is replaced with the second frequency domain coefficient of the frequency domain coefficients to the digital image. Watermark embedding means for embedding a watermark;
A card manufacturing apparatus, comprising: inverse frequency domain conversion means for performing inverse frequency domain conversion on the digital image converted into the frequency domain and embedded with a watermark . Means for generating the watermark comprises:
Means for encrypting the user key;
The card manufacturing apparatus according to claim 1, further comprising means for generating a watermark in the form of a pseudo-random number using the encrypted user key. A black-and-white / color image determining means for determining whether the digital image is a monochrome image or a color image;
When the digital image is a color image,
Color model conversion means for converting the digital image represented by a color model not including a luminance component into a color model including a luminance component, extracting the luminance component of the converted color model, and sending the extracted luminance component to the frequency domain conversion means When,
The digital image converted by the inverse frequency domain conversion means is a luminance component that has been subjected to the inverse frequency domain conversion, and a remaining that has not been subjected to the frequency domain conversion by removing the luminance component from the converted color model. The card manufacturing apparatus according to claim 2 , further comprising color model reverse conversion means for performing color model reverse conversion using the components of the color model. 4. The card manufacturing apparatus according to claim 3 , wherein a position of a watermark embedded in the digital image by the watermark embedding unit is set in advance. 4. The card manufacturing apparatus according to claim 3 , wherein a watermark embedded in the digital image by the watermark embedding unit is embedded together with a specific identifier that designates an embedded position. In the method of producing a card in which information for authentication is embedded,
Converting the card issuing information from the card issuing information and the card authentication information related to the card issuing application into a digital image having a shape of a predetermined size;
Setting the card authentication information of the storage means with a user key, and generating a watermark using the user key;
Embedding the watermark in the digital image;
Printing the watermarked digital image on the card stock,
Embedding the watermark comprises:
Converting the luminance component of the digital image into a frequency domain coefficient divided into two or more regions having at least a first frequency region and a second frequency region;
Of the frequency domain coefficients, the substitution coefficient generated using the first frequency domain coefficient and the watermark is replaced with the second frequency domain coefficient of the frequency domain coefficients to the digital image. Embedding a watermark;
A card manufacturing method , comprising: inverse frequency domain conversion of the digital image converted into the frequency domain and embedded with a watermark . Generating the watermark comprises:
Encrypting the user key;
7. The card manufacturing method according to claim 6 , further comprising: generating a watermark in the form of a pseudo random number using the user key. The digital image is a color image;
Before the method converts the luminance component into a frequency domain coefficient, the digital image represented by a color model that does not include a luminance component is converted into a color model that includes a luminance component, and the converted color model Extracting a luminance component of
After the inverse frequency conversion step, the digital image is subjected to color model inverse conversion using the luminance component and the remaining components that are not subjected to the frequency domain conversion obtained by removing the luminance component from the converted color model. The card manufacturing method according to claim 7 , further comprising a step. The card manufacturing method according to claim 7, wherein the first frequency region is a low frequency region, and the second frequency region is a high frequency region. In the card | curd authentication apparatus manufactured by the card | curd manufacturing method of Claim 7 thru | or 9 ,
Means for scanning the image printed on the card to generate digital image data ;
Means for entering card authentication information from the cardholder;
A watermark generated using the card authentication information input from the card holder;
Authentication determining means for calculating a correlation with a watermark detected using a conversion coefficient obtained by converting the digital image data into a frequency domain, and determining presence / absence of authentication. Card authentication device. The authentication determining means
Watermark generating means for generating a watermark using card authentication information input from the card holder;
Watermark detecting means for detecting and restoring a watermark embedded in the digital image;
11. The card authentication device according to claim 10 , further comprising means for calculating a correlation between the generated watermark and the restored watermark to determine whether or not the card is authenticated. The watermark generating means is
Means for encrypting the card authentication information by setting a user key;
12. The card authentication apparatus according to claim 11 , further comprising means for generating a watermark in the form of a pseudo random number using the encrypted user key. The watermark detection means is
Means for converting a luminance component of the digital image in which the watermark is embedded into a coefficient in a frequency domain;
Means for detecting a watermark embedded in the digital image using the first frequency domain coefficient and the substitution coefficient ;
12. The card authentication apparatus according to claim 11 , further comprising means for authenticating the digital image by obtaining a correlation between the detected watermark and the authentication watermark. A database in which information about the card user is stored;
Means for extracting database search information from the card;
The card authentication apparatus according to claim 12 , further comprising means for searching the database using the database search information and outputting information on the card user. The scanned image includes an identifier indicating a position where a watermark is embedded, and the digital image generating means searches for the identifier and obtains only digital image data in a region defined by the identifier. The card authentication device according to claim 10 . The luminance component of the digital image converted from the card issuing information is converted into a coefficient of a frequency domain divided into two or more regions having at least a first frequency region and a second frequency region, and the frequency region Of the first frequency domain and the watermark generated by using the card authentication information are replaced with the second frequency domain coefficient of the frequency domain coefficients. In the card authentication method produced by the apparatus or method for printing the digital image data embedded with the watermark on the raw material of the card after embedding a watermark in the digital image data,
Scanning the image printed on the card to generate digital image data;
Obtaining digital image data of a region in which a watermark is embedded from the digital image data;
Detecting a watermark from digital image data in an area in which the watermark is embedded;
Entering card authentication information from the cardholder;
Generating a watermark using card authentication information input from the cardholder;
A card authentication method comprising: determining authentication from a correlation between the detected watermark and the generated watermark, and outputting the determined result. The luminance component of the digital image converted from the card issuing information is converted into a coefficient of a frequency domain divided into two or more regions having at least a first frequency region and a second frequency region, and the frequency region Of the first frequency domain and the watermark generated by using the card authentication information are replaced with the second frequency domain coefficient of the frequency domain coefficients. In the card authentication method produced by the apparatus or method for printing the digital image data embedded with the watermark on the raw material of the card after embedding a watermark in the digital image data,
Scanning the image printed on the card to generate digital image data;
Obtaining digital image data of a region in which a watermark is embedded from the digital image data;
Detecting a watermark from digital image data in a region in which the watermark is embedded, and extracting card authentication information from the detected watermark;
Entering card authentication information from the cardholder;
A card authentication method comprising: determining authentication from the correlation between the extracted card authentication information and the input card authentication information, and outputting the determined result.

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