CN111835506B - Information security digital encryption method based on one-time use codebook - Google Patents

Abstract

The invention discloses an information security digital encryption method based on a disposable codebook, which comprises the following steps: the method comprises the steps of utilizing host characteristic information of a file and information special for communication equipment used by the file to form front and back background information, forming a double-track double-block K-group digital vector association structure, extracting part of characteristic information in the background information to serve as a digital key for encrypting plaintext information, adopting a functional dynamic encryption algorithm to encrypt and modulate a symbol dictionary, generating a one-time digital cipher book with the background information, and generating a public digital cipher of the plaintext information. The information security digital encryption method based on the one-time use codebook provided by the invention is organically combined with the SSL/TLS communication protocol encryption system transmitted by the third party, so that the big data and information security in the Internet environment are effectively ensured. The method is suitable for completing the encryption task of the plaintext information by utilizing the characteristic that the private confidential information and the public information are asymmetric under the condition that the background information of the Internet environment is not completely transparent.

Description

Information security digital encryption method based on one-time use codebook

Technical Field

The invention relates to an information security digital encryption method based on a one-time use codebook.

Background

The technology related to the password is various, namely invisible and visible, and digital and non-digital. However, they all share a common feature: digital cryptography is generated around multiple keys generated by a fixed codebook, and there is a close relationship between each of the cryptography.

The general cryptosystem is an information host a of information (message) W, performs public key encryption processing on W to be encrypted by using an encryption algorithm of a symmetric key Q or an asymmetric private key PW and a public key GW, generates a public password MW, and delivers the password MW to a third party C for transmission.

After receiving the encrypted password MW, the access receiver B decrypts the MW by using the private key and a decryption algorithm to restore the information W. (transmitter C: radio delivery/internet delivery).

The most important core method is the generation technology of a fixed codebook used for a plurality of times and a series of encryption technologies generated by the generation technology. Currently there are three types of development:

1. password-based cryptography (PBE-Password Based Encryption) techniques

In order to ensure the flexibility and the security strength of the fixed codebook. A password-based password (PBE-Password Based Encryption) is generated. And generating a symmetric key KEK, and encrypting the information W by the sender A to form a ciphertext MW. After receiving the ciphertext MW, the receiver B decrypts the MW with the symmetric key KEK to restore the information W.

2. Asymmetric cryptography-based (PGP-Pretty Good Privacy) cryptography system

Since symmetric cryptography KEK is easily compromised by third parties, cryptographic software written by Phillips Ji Moman (Philip Zimmermann) individuals in 1990 was improved to asymmetric cryptography-based (PGP-Pretty Good Privacy) cryptography systems.

PGP is currently the most excellent and most secure encryption scheme. Representative software in this regard is PGP encryption software in the united states. The core idea of this software is to protect files with logical partitions, such as logical partition E: is a hard disk partition protected by PGP, then each time the partition is opened, a password is entered to open the partition, and the files within the partition are absolutely secure. When the partition is no longer needed, the partition can be closed and can be made to disappear from the desktop, and when the partition is opened again, a password needs to be input. Without the password, the software developer itself cannot decrypt-! PGP is the most popular file encryption software worldwide. Its source code is public, withstands the cracking challenges of thousands of top hackers, and the fact proves that PGP is currently the safest encryption software in the world. Its only disadvantage is that PGP currently has no official chinese version and that the original version is extremely expensive. Since PGP technology is a technology that the united states national security agency prohibits export.

3. Asymmetric cryptography based (SSL/TLS-Secure Socket Layer/Transport Layer Security) internet cryptography system

SSL/TLS is a cryptographic communication protocol method widely used in Web servers, and is a communication between a client and a server. They all follow a protocol called HTTP (HyperText Transfer Protocol ) for communication. The Web browser is called an HTTP client, and the Web server is called an HTTP server. SSL/TLS is a secure communication technology implemented by combining symmetric keys, public key cryptography, one-way hash functions, message authentication codes, pseudo-random generators, digital signatures, and other technologies in the communication between a Web server and a Web browser. In addition, SSL/TLS may also switch the cipher suite to use a more robust cipher algorithm.

The most important in SSL/TLS systems is the TLS protocol, which is divided into two parts: the TLS recording protocol and TLS handshake protocol.

TLS recording protocol: is responsible for message compression, encryption and data authentication.

TLS handshake protocol: it has 4 sub-protocols: handshake protocol, password specification change protocol, warning protocol, and application data protocol. Handshake protocol: is responsible for negotiating decision cryptographic algorithms and shared keys between the client and the server. Password specification change protocol: is responsible for transmitting a signal for changing the cipher mode to a communication object. Warning protocol: is responsible for communicating errors to the other party when errors occur. Application data protocol: and a protocol for communicating the application data carried on the TLS to the communication object. Wherein the handshake protocol is the focus: after the information exchange between the client and the server is completed, the application data protocol is switched to.

The client obtains the legal public key of the server and completes the authentication of the server.

The server obtains the legal public key of the client and completes the authentication of the client.

The client and the server generate a shared key for use in cryptographic communications.

The client and server generate a shared key for use in the message authentication code.

SSL/TLS is a cryptographic communication scheme that is often used worldwide under today's internet.

With the rapid development of computer technology and digital technology, digital cryptography has also advanced. The main technical direction of the current information data security technology development is as follows: advances in one-way hash function computation technology have evolved toward new encryption algorithms for high-strength one-way hash function values.

1. MD series

MD4 is a one-way hash function designed by Rivet in 1990, capable of producing 128-bit hash values (RFC 1186, revision RFC 1320).

MD5 is a one-way hash function designed by Rivet in 1991, capable of producing 128-bit hash values (RFC 1321). The strong collision resistance of MD5 has been compromised and is currently unsafe.

2、RIPEMD-160

RIPEMD-160 is a one-way hash function designed by Hans Dobbertin, antonon Bosselas and BartPrenee in 1996 that can produce 160-bit hashes.

RIPEMD-160 is also a revision of the RIPEMD one-way hash function designed by the European Union RIPE project. The method comprises the following steps: RIPEMD-128, RIPEMD-256, RIPEMD-320, etc. The strong collision resistance of RIPEMD has been compromised in 2004, but RIPEMD-160 has not yet been compromised. The digital encryption system currently used in bitcoin is RIPEMD-160.

3. SHA series

SHA-1 was designed by NIST (National Institute of Standards and Technology ) in 1993 as a one-way hash function capable of generating 160-bit hash values. As the U.S. Federal information processing Specification (FIPS PUB 180), published as SHA, the revision (FIPS PUB 180-1) published in 1995 was called SHA-1. The NIST then designed a series of SHA as follows:

SHA-256 is capable of generating a 256-bit hash value one-way hash function

SHA-384 is capable of generating 384-bit hash value one-way hash functions

SHA-512 is capable of generating a 512-bit hash value one-way hash function

These one-way hash functions of SHA-2 (SHA-256, SHA-384, SHA-512) were issued in 2002 as a new version (FIPS PUB 180-2) concurrently with SHA-1. The strong collision resistance of SHA-1 has been compromised in 2005, but SHA-2 has not yet been compromised. SHA-3 is the next generation one-way hash function SHA-3 that was developed by NIST (National Institute of Standards and Technology ) beginning in 2005 to replace SHA-1. A one-way hash function algorithm of Keccak was used. Currently, the Internet (SSL/TLS- -Secure Socket Layer/Transport Layer Security cryptosystem mainly adopts the SHA-2 standard.

All of the above cryptographic techniques can be referred to as conventional digital cryptographic techniques, which have the main problems:

1. conventional digital cryptography uses a fixed codebook multiple times.

Defects and deficiencies: security is limited and once a fixed codebook leaks, security fails. The actual requirements of large information quantity and quick change in modern times cannot be met.

2. Conventional digital cryptography uses specialized one-way hash functions, and hash values employ fixed-length binary bits, such as 128 bits, 256 bits, etc., of SHA-2, with a maximum of 512 bits, although SHA-3 alone may not be limited in length. Defects and deficiencies: is regulated by international export, and has high cost.

3. The above conventional digital cryptography methods are all single structures employing a single digital unit.

Defects and deficiencies: the encryption key is generated independently of the background information of the encrypted information W.

The secondary problems are:

1. the traditional password method adopts the following steps:

the encryption processing is directly carried out on the information W, and the encryption method is only related to W and is irrelevant to technical parameters of a Client browser end and a Server end of transmission communication equipment.

2. The traditional password method adopts the following steps:

the encryption processing is directly carried out on the information W, and the encryption method is only related to the W and is irrelevant to the background information of the information host A and the information access receiver B.

Disclosure of Invention

The invention provides an information security digital encryption method based on a disposable codebook, which is organically combined with a third party transmission SSL/TLS communication protocol password system to completely solve the problem of big data and information security in an Internet environment. The invention adopts the following technical scheme for realizing the purposes:

the invention discloses an information security digital encryption method based on a disposable codebook, which comprises the following steps: the method comprises the steps of utilizing host characteristic information of a file and information special for communication equipment used by the file to form front and back background information, forming a double-track double-block K-group digital vector association structure, extracting part of characteristic information in the background information to serve as a digital key for encrypting plaintext information, adopting a functional dynamic encryption algorithm to encrypt and modulate a symbol dictionary, generating a one-time digital cipher book with the background information, and generating a public digital cipher of the plaintext information.

The information security digital encryption method based on the one-time use codebook provided by the invention is organically combined with the SSL/TLS communication protocol encryption system transmitted by the third party, so that the big data and information security in the Internet environment are effectively ensured. The method is suitable for completing the encryption task of the plaintext information by utilizing the characteristic that the private confidential information and the public information are asymmetric under the condition that the background information of the Internet environment is not completely transparent.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate and do not limit the invention, and together with the description serve to explain the principle of the invention:

FIG. 1 is a block K-group random feature number vector correlation body with double tracks and double granules according to an embodiment of the invention

Is a working principle diagram of the (c).

FIG. 2 is a private secret digital key of an embodiment of the present invention

Modulation schematic.

FIG. 3 is a private public digital key of an embodiment of the present invention

Modulation schematic.

FIG. 4 shows the embodiment of the invention with prospect

Public digital password of characteristic KeyW (x)/PassW (x)

Modulation schematic.

Detailed Description

The present invention will now be described in detail with reference to the drawings and the specific embodiments thereof, wherein the exemplary embodiments and descriptions of the present invention are provided for illustration of the invention and are not intended to be limiting.

Examples:

basic concept and mathematical principle of digital encryption modulation algorithm

1. Monorail K granule digital vector unit:

assume that

The method is an L-dimensional positive integer digital vector group with the digital length of M bits and the metering system unit of L, and can be divided into K groups.

When K is more than 1, the method comprises the steps of,

namely an L-dimension digital vector unit of a single-track K granule:

is a digital vector group composed of positive integer digital information.

It can be noted that:

when k=1, _a->

The transformation into a common monorail L-dimensional vector +.>

Is a positive integer number set.

2. Double-track K-block digital vector correlation body:

assume that

The number length is M bits, the metering system unit is L, and the two L-dimensional positive integer number vector groups can be divided into K groups:

is composed of

Double-track K-block digital vector correlation body: />

3. Double-track single-block digital vector correlation body

Assume that

The number length is M bits, the metering system unit is L, and the metering system unit can be divided into two L-dimensional positive integer number vector groups of K groups. In particular, when k=1, at +.>

In the process, the liquid crystal display device comprises a liquid crystal display device,

wherein (1)>

Are all normal L-dimensional positive integer digital vectors.

Weighing scale

The vector correlation body is an L-dimensional double-track single-block digital vector.

4. Parameter-free double-rail single-block digital vector correlation body:

and (3) making:

for origin, ++>

Is a moving point.

Then

Is a two-track single-block digital vector correlation body, and forms a plane called a digital cipher plane MMS in an L-dimension digital vector space. In MMS plane there is a concomitant L-dimensional double-track single-block digital vector correlation body +.>

A is called an associated matrix, and +.>

Let B be the derivative matrix, and +.>

Thus, it is called

Is->

Non-parameter associated digital vector correlation body

Weighing scale

Is->

Non-parametric derived digital vector correlation body

From derived transformations

Namely: />

The encryption function of the digital password is realized.

5. Double-track double-block K grouping digital vector correlation body:

assume that

The number length is M bits, the metering system unit is L, and the metering system unit can be divided into two L-dimensional positive integer number vector groups of K groups. If not specified otherwise, in the following, M.ltoreq.13, l=10, 1 is assumed < L < +++ and L is a positive integer. When k=2, by +.>

The formed association body is used for: />

To represent. Here:

assume that:

is the (foreground) first number vector, < ->

For the (background) second digital vector, W (x) is the plaintext of the information.

For the sake of simplicity the device is designed to be,

definition 1:

use->

Representing a set of background parametric information digital vectors representing the foreground.

Definition 2:

use->

Representing a digitally encoded vector set representing the character set of the information W (x) that needs to be encrypted.

Definition 3:

use->

And representing the background parameter information digital vector group representing the background.

Definition 4:

use->

Representation, representing addThe background keyword Key W (x)/PassW (x) character set of the secret control process is a digital coding vector group.

Thus, the first and second substrates are bonded together,

at->

In the case of a change in the background B and a further subdivision into groups K-1, then +.>

While the changes constitute K-1 subpackets. At this time, by +.>

The formed association body can be used

To represent. Then, there are:

and call->

Grouping the digital vector correlation bodies for the double-track double-granule K,

the method is characterized by comprising the following steps:

wherein->

Is the kth packet.

Encryption modulation algorithm of information plaintext W (x)

General function word cipher book

Modulation of (2)

Assume that

The number length is M bits, the metering system unit is L, and the two L-dimensional positive integer number vector groups can be divided into two groups of K groups. At this time, by +.>

The digital vector correlation body is formed: />

Definition 5: v is a vector consisting of 2 numbers

The dimension of the metric space is L. V can be divided into independent subspaces V ₁ ，V ₂ ，…V _i ，…V _K ，V _i Is the V i-th subspace (i=1, 2, …, K).

Definition 6: let t denote the vector

The subscript value of the metric space V is formed and B is used ₁ ，B ₂ ，B ₃ ，…，B _k-1 ，B _k Representing each subspace V _i The maximum value of the subscript (i=1, 2, …, K, l=b _K )。

Definition 7: by m _i ＝B _i -B _i-1 (i=1, 2, …, K) denotes subspace V _i Is a dimension of (c). And at t E (B) _i-1 ，B _i ]On each subspace of (2), there is m ₁ ＝B ₁ ，m ₂ ＝B ₂ -B ₁ ，...，m _K ＝B _K -B _K-1 ，(B _K ＝L，1≤t≤L)。

When M is less than or equal to 13 and l=10, the method comprises the following steps of

The composed double-track double-group K grouping digital vector correlation body is as follows:

and has the following components: t is more than or equal to 1 and less than or equal to L

Deriving a cryptographic transformation: v (t) =p (t) +q (t)

Derivative digital vector:

functional derived cryptographic transformations:

functional derivative digital vector:

in particular: in last bit vector subspace V _K And (3) the following steps: m is m _K ＝N，τ∈(B _K-1 ，B _K ](τ=0, 1,2, …, N) and

and (3) performing linear transformation: p (P) _WZ (B _K-1 +1+τ)＝MB(τ)(t＝B _K-1 +1+τ) then creates a new double track double block K grouped digital vector correlation:

a high-dimensional one-way hash functional power algorithm DMAC (c) is adopted for encoding the dictionary +.>

Modulating to obtain->

The functional derivative 1-1 corresponds to the transformation. Thereby generating a new alphanumeric code mapping relationship: />

Thus creating a new digital codeDictionary:

thus, it is called a generalized function word codebook:

note 1: MB (τ) is a character encoding dictionary

UTF-8/16 unified digital coding of character No. tau, Z (tau);

and (2) injection: DMAC (c) is a special one-way hash functional power calculation method;

and (3) injection: v (V) _WZ RTMB (τ) as a correlator

The value at point τ.

Random generalized function word cipher book

New generated universal function word cipher book

In the modulation process of (2) the association->

Background conditions of (2):

is fixed. But when local digital vector is taken +.>

Is a pseudo-random number subspace

And then generating a double-track double-granule K grouping random number vector correlation body: />

Digital code book->

The digital codebook with random parameter R is modulated:

therefore, it is called random generalized function word codebook

And (4) injection:

as pseudo-random number vectors, RND (x) is a pseudo-random function.

Disposable digital cipher book

The first party (information host A) encrypts the information plaintext W (x) to be kept secret, and then generates a digital password file MW (x) for storage. When the second party (information access person B) needs to make an information access, the digital password MW (x) is transmitted to the second party (information access receiver B) by the third party (intermediate person C). The context conditions are formed by a series of associated information such as A, B, C and the environment D where ABC is located:

plus pseudo-random number space->

Then a uniquely determined encryption condition is constituted that is only related to ABCD:

under the condition, communication characteristic authentication information of a third party C/S is added>

Constitute the double track double group K group random number vector correlation body:

the notation dictionary is +.>

Modulating, thereby producing a random generalized function word codebook with third party authentication:

the method is called as: disposable digital cipher book

And (5) injection: r represents a random parameter;

and (6) injection: t represents the band pass authentication parameter.

FIG. 1 is a block K-group random feature number vector correlation body with double tracks and double granules according to an embodiment of the invention

Is a working principle diagram of the (c).

Definition 8: (digital code) a one-time use digital code book:

after generation. Ming dynastyThe word W (x) is in the digital codebook +.>

In (a) the corresponding value->

A digital cipher called plaintext W (x).

Definition 9: (private digital password) when

When the private information is the private information, the private digital codebook is as follows: />

Plaintext W (x) is in digital codebook +.>

In (a) the corresponding value->

A private digital password called plaintext W (x).

Definition 10: (public digital code) when

When the public information is the public information, the public digital code book is as follows: />

Plaintext W (x) is in public digital codebook +.>

In (a) the corresponding value->

A public digital cipher called plaintext W (x).

Private secret digital key

And private public digital key->

In the digital codebook:

in the modulation process of (1), the double-track double-block group K-1 grouping digital vector association condition is utilized:

constitute general digital association->

Performing first modulation by adopting functional power algorithm DMAC (c) to generate universal digital codebook +.>

Constructing a digital vector ++with a foreground according to a special rule by using the foreground condition>

Special text Key W (x) for keywords, digital codebook +.>

Generating a key number vector private digital password corresponding to the Key W (x)>

Definition 11: here, the

Corresponding to PW (x), called private secret digital key, noted +.>

FIG. 2 is a schematic illustration of the present inventionEmbodiment private secret digital key

Is a modulation scheme of (a)

Will be

Digital vector +.>

Another part of information->

Thus, a new vector with the foreground number is generated +.>

Double-track double-granule K grouping digital vector correlation body with key character:

DMAC (c) versus symbol dictionary employing functional power algorithm

And re-modulating the second time. Obtaining a new one-time use vector with a foreground number +.>

Digital codebook of key feature information:

thus, at codebook->

The foreground number vector ++of the password PassW (x) is generated in>

Private public digital code of features->

Definition 12: here, the

Corresponds to GW (x), called private public digital key, denoted as +.>

Thus, the first and second substrates are bonded together,

key digital vector encryption information (private secret digital key) which is the most important for the password PassW (x) to complete the encryption task. In turn->

Becomes the private public digital key of W (x).

FIG. 3 is a private public digital key of an embodiment of the present invention

Is a modulation scheme of (a)

Private public digital key

And public digital code->

Is of (a) associated modulation

Definition 13: when (when)

Is a public foreground digital vector->

When (I)>

When->

Key W (x) is defined by +.>

When the key W (x) and the passW (x) are combined, the generated public digital code +_>

With->

Is a private feature of (a). It is called a public digital code, noted: />

From the definition above alone:

and->

There is no association. Only foreground condition->

And->

Is different in value. But in the actual encryption modulation process, the background condition is adopted>

To change the personality modulation of

And->

Is a relationship of association of the above. Thereby realizing the modulation function of (private/public) associated encryption. The specific implementation process is as follows:

grouping the private digital vector correlation bodies with double-track double-granule K:

DMAC (c) adopting functional power algorithm for character dictionary +.>

The first modulation is performed. Generating a private universal digital codebook: />

In the foreground condition->

A set of key keys w (x) is extracted. Utilize private digital codebook->

Private secret digital key modulated to W (x)>

Reuse->

Calculating as parameters, partially replacing the correlation body->

Is->

Namely: />

The functional power algorithm DMAC (c) is adopted for the word dictionary +.>

Performing a second modulation, thereby generating a new one-time-use private digital codebook with foreground features>

The private public key +_of the password PassW (x) can thus be modulated out>

In public digital ciphers

In the modulation process of (2) with private public digital key->

Calculating as public parameter to replace partial public double track double block K group digital vector relation body ∈>

In (a) and (b)

Namely: />

The functional power algorithm DMAC (c) is adopted for the word dictionary +.>

The third modulation is carried out, thereby generating a new disposable with prospect +.>

Public digital codebook of keyword Key W (x) and password PassW (x)>

Thereby modulating the product with prospect +.>

Public digital code of plaintext information W (x) of feature KeyW (x)/PassW (x)>

FIG. 4 is a public digital code of an embodiment of the present invention

Is a modulation scheme of (a)

Due to

Is->

Use of foreground vector +.>

Key w (x) and pass word PassW (x). Public digital code->

With the private feature of plaintext W (x). Thereby realizing private public digital key +>

And public digital code->

Is a modulation of the correlation of (a).

Digital cipher decryption algorithm for digital cipher MW (x)

Information host A is required in different places or at different timesWhen decrypting digital cipher MW (x), firstly obtaining public digital cipher

After this, a private secret digital key +.>

Modulating private public digital key with private key and password KeyW (x)/PassW (x)>

To->

Calculating as public parameter to replace partial public double track double block K group digital vector relation body ∈>

Is->

Namely:

thereby generating a one-time-use digital cipher +_ with private key>

Public digital codebook of key features +.>

Then receive the public digital code +.>

Using character dictionary->

The digital comparison calculation is carried out to obtain

The corresponding UTF-8/16 is coded uniformly. Thereby, the information plaintext W (x) is restored, thereby realizing the information plaintext W (x) by the public password +.>

Decryption to W (x).

The foregoing has described in detail the technical solutions provided by the embodiments of the present invention, and specific single examples have been applied to illustrate the principles and implementations of the embodiments of the present invention, and the description of the above embodiments is only suitable for helping to understand the principles of the embodiments of the present invention; meanwhile, as for those skilled in the art, according to the embodiments of the present invention, there are variations in the specific embodiments and the application scope, and the present description should not be construed as limiting the present invention.

Claims (3)

1. An information security digital encryption method based on a disposable cipher book is characterized by comprising the following steps:

the number length is M bits, the metering system unit is L, and the two L-dimensional positive integer number vector groups can be divided into K groups:

by->

Constitute a double track K group digital vector correlation body:

the digital information of the information host A forms a foreground condition:

the information receiver B, the transmission third party C/S and the digital information of the communication network environment D construct the background condition according to a certain rule: />

Plus pseudo-random number vector subspace->

Constructing a joint encryption condition->

Communication characteristic authentication digital information added with third party C/S>

K grouping random number vector correlation body for forming double-track double-group>

The notation dictionary is +.>

Modulating, thereby producing a random digital codebook with third party authentication,

i.e. one-time use digital codebook:

wherein the information plaintext W (x) is in the digital code book

Corresponding value +.>

Is a digital cipher of the information plaintext W (x).

2. The one-time-use-codebook-based information security digital encryption method as defined in claim 1, wherein:

using the double-track double-block K-1 grouping digital vector association condition:

constructing a random number vector correlation body: />

Performing first modulation by adopting a functional power algorithm DMAC (c) to generate a random universal digital codebook:

use prospect condition:

constructing the vector with the foreground number according to a specific rule>

Special text Key W (x) of keyword, using universal digital codebook +.>

Generating a key digital vector private digital key corresponding to KeyW (x)

Will->

Digital vector +.>

Another part of information,/i>

Thereby generating a new vector with foreground digits +.>

Double-track double-granule K grouping digital vector correlation body with key character:

the notation dictionary is +.>

Performing secondary modulation to obtain new one-time used digital vector ++>

Digital codebook of key information:

thereby modulating the private public digital key of the password PassW (x)>

3. The one-time-use-codebook-based information security digital encryption method as defined in claim 2, wherein:

in the foreground condition

Extracting a group of key words KeyW (x), and utilizing private digital codebook +.>

Private public digital key modulating the password PassW (x)>

To->

Calculating as public parameter to replace partial public double track double block K group digital vector relation body ∈>

Is->

Namely:

the functional power algorithm DMAC (c) is adopted for the word dictionary +.>

Performing a third stepSecondary modulation to produce a new one-time use with private public digital key

Public digital codebook->

Public digital password for generating plaintext information W (x)

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