JP3549657B2 - Private key retention management method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for holding and managing a secret key in secure communication by a public key method, and in particular, divides a decryption key of a secret key conventionally stored in each user's computer, and partially divides the decryption key into a communication partner (transmission (A person who needs to confirm the source) and an arbitrary information processing device.
[0002]
[Prior art]
2. Description of the Related Art Today, with the development of computers, electronic communication via a communication network has been remarkably developed. In particular, recently, electronic communication using a communication network accessible by an unspecified number of users (in this specification, such an open communication network is referred to as an open network) has significantly increased.
[0003]
In particular, recently, a membership-based sales system using the open network has been increasing. In such a membership sales system, a transaction form in which a product order is received by computer communication and the product is mailed to the member who ordered the product has been widely adopted.
[0004]
In addition, a so-called electronic payment method that allows a credit card to be deducted from a person's credit account with the consent of the person through computer communication has come into practical use.
[0005]
In the era of free trading through such an open network, it is important to confirm which user (member) has sent an order for a product by computer communication or a consent for direct debit. . In particular, the open network is a communication system with a huge number of communication destinations and those who have sent communication messages (messages by digital signals, including both ciphertexts and unencrypted plaintexts). This problem is even more important because the face cannot be identified.
[0006]
For example, if a third party impersonates a legitimate user and illegally sends an order for a product or accepts a direct debit in a communication message and cannot immediately detect this, the business community will be greatly affected. Needless to say, it causes confusion.
[0007]
For this reason, various methods for confirming a communication partner in electronic communication have been proposed. Among these methods of confirming a communication partner, a method called a “public key” method is considered to be promising.
[0008]
FIG. 2 schematically shows a method of concealing and authenticating a communication message by the "public key" method.
In FIG. 2, it is assumed that a user 1, a seller 2, and a credit company 3 perform computer communication with each other.
[0009]
The user 1 has a public key P-Key-U disclosed to the seller 2 and the credit company 3, and a secret key S-Key-U known only to the user.
[0010]
The seller 2 has a public key P-Key-M disclosed to the user 1 and the credit company 3 and a secret key S-Key-M known only to himself / herself.
[0011]
The credit company 3 has a public key P-Key-C disclosed to the user 1 and the seller 2, and a secret key S-Key-C known only to itself.
[0012]
The public key and the secret key are in a relationship that can mutually decrypt another encrypted one. That is, in the case of the user 1, what has been encrypted with the secret key S-Key-U of the user 1 can be decrypted with the public key P-Key-U of the user 1. Conversely, what has been encrypted with the public key P-Key-U of the user 1 can be decrypted with the secret key S-Key-U of the user 1. This relationship can be applied to the public key and the private key of the seller 2 and the credit company 3.
[0013]
Next, a method of concealing and authenticating a communication message using the public key and the secret key will be described.
First, the seller 2 encrypts the product information with the public key P-Key-U of the user 1 and sends it to the user 1 (step S200). On the other hand, when the user 1 places an order for a predetermined product, the user 1 encrypts his / her ID information with the secret key S-Key-U in the sense that he / she has made an order, and puts it in the plaintext of the product order. Add. Further, in order to prevent the information of the product order from being read by a third party, the entirety of the product order to which the ID information has been added is encrypted by the public key P-Key-M of the seller 2, and this is encrypted by the seller 2 (Step S210).
[0014]
The seller 2 receiving the communication message of the product order first decrypts the communication message with his / her private key S-Key-M. However, since the ID information encrypted by the secret key S-Key-U of the user 1 cannot be decrypted by the secret key S-Key-M of the seller 2, the seller 2 subsequently determines the part that could not be decrypted. The decryption is performed using the public key P-Key-U of the user 1.
[0015]
As a result, when the ID information of the user 1 is correctly decrypted, the seller 2 has the private key S-Key-U whose sender is paired with the public key P-Key-U of the user 1. You can check that.
[0016]
Since the user having the public key P-Key-U and the secret key S-Key-U is nothing but the user 1, the seller 2 confirms that the sender of the communication message is the user 1. be able to.
[0017]
The above is the method of concealing and authenticating communication messages by the public key method.
[0018]
After performing the above-described identity verification, the seller 2 checks with the credit company 3 whether or not credit sales are possible. That is, the seller 2 encrypts the communication message for inquiring of the credit sale to the user 1 with the public key P-Key-C of the credit company 3 so that the contents are not known to a third party. (Step S220).
[0019]
Upon receiving this inquiry, the credit company 3 decrypts the communication message with its own secret key S-Key-C, refers to a database or the like (step S230), and compares the result with the public key P-Key of the seller 2. Return by encrypting with M (step S240).
[0020]
Seller 2 decrypts the response to this inquiry with its own private key S-Key-M, encrypts the result again with user 1's public key P-Key-U, and sends it to user 1 (step S200).
[0021]
According to the above method, the seller 2 can safely confirm the user 1 unless the contents of the communication message are known to a third party and the secret key S-Key-U of the user 1 is stolen. Can be.
[0022]
However, the secret key S-Key-U of the user 1 is usually stored in the computer of the user 1, and there is a possibility that the secret key S-Key-U may be stolen or misused by a third party.
[0023]
Therefore, various methods for holding and managing the secret key in the public key method have been conventionally proposed.
[0024]
As a conventional technique closest to the technique of the present invention, a concept has been proposed in which a private key is encrypted and stored by a strong method, and a decryption key for decrypting the private key is divided and possessed.
[0025]
By doing so, even if a third party steals an encrypted private key, it cannot directly decrypt it, and a third party must obtain a decryption key to use the private key. Must. However, since the decryption key is divided and managed, theft is extremely difficult.
[0026]
As a method of dividing and managing the decryption key, specifically, a method of dividing the decryption key into an access passphrase and auxiliary information and storing the auxiliary information in an IC card, and a method of storing fingerprints, voices, faces, etc. A method has been proposed in which data is used as auxiliary information for identity verification.
[0027]
[Problems to be solved by the invention]
However, the method of dividing the decryption key of the secret key and storing a part of the decryption key on an IC card is a method in which when a person who knows the passphrase in some way steals the IC card of the passphrase user, It is no longer possible to detect unauthorized authentication.
[0028]
Also, in the above-mentioned method using an IC card, in a situation where the number of communication groups is expected to increase in the near future, it may occur that an IC card must be created and stored for each communication group. Involves the complexity of managing a large number of IC cards. If a large number of IC cards are lost at one time, the user has to notify each communication group of the invalidity of the IC cards, resulting in great confusion.
[0029]
Also, the method of storing a part of the decryption key on an IC card requires that a dedicated IC card reader be provided on the user side, and that a different IC card reader be provided depending on the type of IC card. In consideration of the above, capital investment is significantly increased as a whole.
[0030]
On the other hand, the method of using the data of fingerprints, voices, faces, and the like as auxiliary information for personal identification also leaves the possibility of falsifying the data of the fingerprints, voices, faces, and the like of the individual by some method.
[0031]
Also, the point that an auxiliary device for reading and confirming data such as fingerprints, voices, and faces is required is the same as the method of the IC card.
[0032]
Therefore, the problem to be solved by the present invention is that the secret key cannot be decrypted only by the user's passphrase, and the rest of the decryption key does not exist on the user's side, so that theft is difficult. An object of the present invention is to provide a method for holding and managing an authentication secret key having an impossible decryption key.
[0033]
Further, the present invention solves the complexity of the device and the complicated management that may occur in the future due to the conventional means for authentication such as an IC card, and the simple management of the decryption key is performed only by the existing computer device. It tries to realize the method.
[0034]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a private key holding and managing method according to claim 1 of the present application comprises:
In the method for holding and managing a secret key in secure communication by a public key method, each secret key user's computer
After using the secret key, generating a scramble key from the access passphrase and predetermined information, encrypting and storing the secret key with the scramble key,
A process of sending predetermined information for synthesizing the scramble key to a communication partner and extinguishing it from its own computer;
A process of receiving the predetermined information by sending an access passphrase to the communication partner at the next use of the secret key;
Restoring the scramble key from the access passphrase and the predetermined information, thereby decrypting the secret key;
And processing for generating a scramble key again after use and encrypting and storing the secret key.
[0035]
Next, the private key holding and managing method according to claim 2 of the present application is the method according to claim 1, wherein
The predetermined information for synthesizing the scramble key together with the access passphrase is non-fixed information temporarily generated at the end of use of the secret key.
[0036]
According to a third aspect of the present invention, in the method of the second aspect, the non-fixed information is a random number generated by a computer of a communication party, a random input by a keyboard, and a time. It is characterized by comprising one of the outputs of the function.
[0037]
According to a fourth aspect of the present invention, in the method of the first aspect, the communication partner storing the predetermined information for synthesizing the scramble key is an arbitrary communication partner specified by a user or an information processing device. It is characterized by having.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of a method for holding and managing a secret key in a public key system according to the present invention will be described below with reference to the accompanying drawings.
[0039]
FIG. 1 shows a processing flow of a secret key holding and managing method according to the present invention.
The private key retention management method of the present invention is based on the “public key” method described above, and a user has a public key that is disclosed in a communication group and a private key that only the user knows.
[0040]
The secret key is encrypted by a method described later and stored in a user's computer or the like. The secret key encrypted for storage is distinguished from an unencrypted secret key and is referred to as a storage private key.
[0041]
The private key holding and managing method according to the present invention preferably stores the private key in a different form each time the private key is used. In other words, the stored secret key at the start of use is different from the stored secret key at the start of previous use. In this case, therefore, a different key is used each time to decrypt the stored secret key at the start of use of each secret key.
[0042]
In the method of the present invention, the key for decrypting the storage private key can decrypt the private key in the same manner as a normal decryption key, and can also encrypt the private key. A key that can be used for both encryption and decryption is referred to as a scramble key here in distinction from a normal decryption key.
[0043]
In the secret key holding / managing method according to the present invention, a decryption key (corresponding to the above-mentioned scramble key) for decrypting a stored secret key is divided and stored in different locations. A characteristic feature is that part of the scramble key is not present near the user.
[0044]
Specifically, the user stores only the access passphrase as a part of the scramble key, sends the rest of the scramble key to the communication partner, stores it, and obtains the scramble key when using it to synthesize the scramble key .
[0045]
Hereinafter, the processing according to the method of the present invention will be described with reference to FIG. Note that the processing in FIG. 1 is all processed in the user's computer except for transmission from a communication partner.
[0046]
First, the stored private key when the user tries to use the private key is encrypted and stored by the scramble key generated at the end of the previous use of the private key, as described later. This stored private key at the start of use of the private key is referred to as a stored private key at the start of use to distinguish it from the stored private key at the end of use. The scramble key used to encrypt the storage secret key at the start of use, that is, the key for decrypting the storage secret key at the start of use, is referred to as a first scramble key.
[0047]
When trying to use a secret key, the user first enters an access passphrase into his computer (step S10). This access passphrase is sent to a communication partner through a communication line. At this time, the access passphrase is preferably transmitted by being encrypted with the public key of the communication partner.
[0048]
The communication partner that has received the access passphrase returns the first random number generated at the end of the previous use described later to the user (step S20).
[0049]
The access passphrase and the first random number each constitute a part of the first scramble key, and the user's computer synthesizes the first scramble key therefrom (step S30). The first scramble key synthesized here is used to encrypt the secret key at the end of the previous use of the secret key.
[0050]
Next, using the first scramble key, the stored secret key at the start of use is decrypted, that is, an unscramble process is performed (step S40).
[0051]
As a result, an unencrypted secret key can be obtained (step S50).
[0052]
Using the unencrypted secret key, the user can decrypt the cipher text or encrypt his / her ID information for authentication (step S60).
[0053]
Here, a case will be described in which user ID information is encrypted using a secret key. More specifically, as described above, the own ID information encrypted with the secret key is added to the plain text (text), and the entire communication message including the ID information is encrypted with the public key of the other party and transmitted.
[0054]
The communication partner that has received the encrypted communication message can decrypt the communication message encrypted with its own (the communication partner here) public key using its own private key. The communication message is decrypted using the secret key.
[0055]
However, since the user ID information encrypted by the user's private key cannot be decrypted by the communication partner's private key, the communication partner transmits the part that could not be decrypted to the user's public key. For further decoding.
[0056]
If the user's public key successfully decrypts the user's ID information, this ensures that the sender is using the private key that is paired with the public key, ie, that he is a legitimate user Can be confirmed.
[0057]
Thus, the communication partner performs necessary procedures, for example, debiting the user's account.
[0058]
After using the secret key, the user's computer generates a second random number (step S70).
[0059]
From the second random number and the access passphrase, the user's computer synthesizes a second scramble key (step S80). Using this second scramble key, the user's computer encrypts the secret key (step S90) and stores it as a storage private key at the end of use (step S100). The secret key is encrypted by an encryption method that is almost impossible to decrypt, for example, a method called hashing.
[0060]
After storage, the second scramble key is deleted.
[0061]
On the other hand, the second random number generated in step S70 is encrypted with the communication partner's public key (step S110), and sent to the communication partner as an encrypted random number (step S120).
[0062]
After generating the encrypted random number, the second random number is deleted from the user's computer.
[0063]
The second random number sent to the communication partner is decrypted by the communication partner and stored until the next use of the secret key. The second random number stored by the communication partner becomes a part of the key for decrypting the user's stored secret key.
[0064]
When the next secret key is used, the communication partner sends the above-mentioned second random number to the user, on condition of the user's request and input of the access passphrase. In the flowchart of FIG. 1, the second random number is the first random number when the user uses the next secret key.
[0065]
Subsequent processing on the user side is the repetition of steps S10 to S120.
[0066]
The above is the outline of the method for holding and managing the secret key when the secret key is continuously used. However, the first use of the secret key is performed in the middle of the normal process, that is, when the process from step 70 is performed. Good.
[0067]
That is, at the time of using the secret key for the first time, after using the secret key, the user inputs his / her own access passphrase (step S10), and generates a second random number by a computer (step S70). A scramble key is generated (step S80). Thereafter, the secret key is encrypted with the second scramble key (step S90) and stored as a storage secret key at the end of use (step S100), as in the above-described normal processing. It encrypts with the key (step S110) and sends it to the communication partner as part of the decryption key when the next private key is used (step S120).
[0068]
By using the above-described secret key for the first time, the secret key can be held and managed by the normal processing thereafter (steps S10 to S120).
[0069]
According to the secret key holding / managing method of the present invention, stealing of the secret key can be almost completely prevented. This is because part of the information of the decryption key does not exist near the user.
[0070]
The stored secret key is encrypted by a method that is almost indecryptable, such as hashing, as described above. Therefore, even if the third party steals the stored private key itself, it cannot decrypt the private key. To decrypt this private key, a third party must obtain both the stored private key and the decryption key.
[0071]
However, according to the method of the present invention, a part of the decryption key corresponding to the first random number and the second random number does not exist near the user including the user's computer file. On the other hand, the access passphrase is in the user's memory and cannot be stolen. Eventually, the third party cannot obtain the decryption key and therefore cannot decrypt the private key.
[0072]
Thus, theft and misuse of the authentication secret key can be almost completely prevented.
[0073]
Another feature of the secret key holding and managing method according to the present invention is that a decryption key for decrypting a stored secret key can be an intangible one (access pass phrase + random number).
[0074]
By using the decryption key as (access passphrase + random number), even when the number of open networks increases, the management of the authentication secret key can be made simple and clear.
[0075]
That is, for example, in the conventional method of managing a part of a decryption key by an IC card, as the number of communication groups of the open network increases, the number of secret keys and the number of IC cards increase accordingly. In the near future, the number of open network communication groups is expected to increase sharply. Therefore, in the conventional IC card method, a large number of IC cards must be possessed, and these managements become complicated.
[0076]
On the other hand, according to the method of the present invention, it is possible to possess many secret keys using one access passphrase and many random numbers. That is, by storing only one access passphrase, the user can completely manage many decryption keys and secret keys.
[0077]
As a result, even in a situation where the number of private keys increases, it is possible to realize extremely simple and clear possession of the private keys.
[0078]
Furthermore, since the decryption key is intangible, the method of the present invention can simplify various devices for restoring the decryption key, which contributes to simplification of the device.
For example, a conventional method of using an IC card as an auxiliary means for authentication, a method of using a fingerprint as an auxiliary means for authentication, and a method of using face data as an auxiliary means for authentication include an IC card reader, a fingerprint recognition device, and a camera, respectively. Auxiliary equipment such as is required.
[0079]
Providing such an auxiliary device in every user's computer requires a huge capital investment as a whole society, considering the penetration of open systems.
[0080]
On the other hand, according to the method of the present invention, it is sufficient to use an existing computer system, and no new capital investment is required.
[0081]
Finally, according to the method for holding and managing the secret key for authentication of the above embodiment, in the event that the secret key is misused, the user can know that the secret key has been stolen.
[0082]
That is, in the method of the above embodiment, a part of the decryption key held by the communication partner changes each time the secret key is used. If the private key is stolen and misused in any way, the user will not be able to use the secret key the next time he tries to use it because the decryption key has already been changed by the use of a third party. You can immediately know that the key has been compromised and take the next best thing.
[0083]
Considering that the amount of a single transaction is usually limited in transactions over an open network, the method according to the present invention makes it possible to reduce the damage when a secret key is stolen to a certain limit or less. Become.
[0084]
The description of the above-described embodiment is completed above, but the gist of the present invention is not limited to the above-described embodiment, and includes superordinate concepts, replacement of equivalents, and the like. These are described below.
[0085]
In the above embodiment, a part of the decryption key is a random number generated by a computer, and the decryption key is changed each time it is used. However, the superordinate concept of the present invention is to have a communication partner keep a part of the decryption key, and includes a case where a part of the decryption key always has a fixed shape.
[0086]
In this way, even with a method of depositing a part of the decryption key in the communication partner, the private key can be held and managed with high reliability, and a simple management method of a large number of private keys and a simple device configuration can be realized. Can be.
[0087]
In the above embodiment, a part of the decryption key is a random number generated by the user's computer. However, the present invention is not limited to the random number, but may be information generated temporarily. The extraordinarily generated information may be, for example, a random keyboard input by the user, an output of a function that changes with time, and the like.
[0088]
Further, as a modification of the method of not placing a part of the decryption key near the user, for example, instead of sending a part of the decryption key to a communication partner, an information processing device arbitrarily designated by the user, It is also possible to send the information to a three-party information processing device or the like.
[0089]
Although the above description has been made with consideration of commerce in an open system, the method of the present invention is not limited to commerce but can be applied to all communication partner confirmations via computer. For example, the present invention can be applied to identification of a person in administrative procedures, such as issuance of a resident's card, which will be realized in the future, and identification of a patient in receiving and transmitting medical data such as patient data and prescriptions.
[0090]
【The invention's effect】
As is apparent from the above description, according to the method for holding and managing a secret key according to the present invention, the secret key cannot be decrypted only by the passphrase of the user, and the remaining of the decryption key remains near the user. By eliminating the portion, secure communication by the public key method in an open system in which the secret key cannot be stolen or misused can be realized.
[0091]
Further, according to the present invention, the reading device required by the conventional authentication method using an IC card or the like can be omitted, and the existing computer system can be used as it is, and the secure communication using the simple public key system with a simple device configuration can be performed. Can be realized.
[0092]
Further, even when the number of secret keys becomes large, a method of managing and holding all secret keys can be provided by managing a single access passphrase.
[Brief description of the drawings]
FIG. 1 is a flowchart showing the flow of processing in a secret key retention management method according to the present invention.
FIG. 2 is a flowchart conceptually showing a method of identity verification using a public key method.
[Explanation of symbols]
1 User 2 Seller 3 Credit company P-Key-U User's public key S-Key-U User's private key P-Key-M Seller's public key S-Key-M Seller's private key P-Key- Public key of C credit company S-Key- Private key of C credit company

Claims (4)

In the method for holding and managing a secret key in secure communication by a public key method, each secret key user's computer
After using the secret key, generating a scramble key from the access passphrase and predetermined information, encrypting and storing the secret key with the scramble key,
A process of sending predetermined information for synthesizing the scramble key to a communication partner and extinguishing it from its own computer;
A process of receiving the predetermined information by sending an access passphrase to the communication partner at the next use of the secret key;
Restoring the scramble key from the access passphrase and the predetermined information, thereby decrypting the secret key;
And a process of generating a scramble key again after use and encrypting and storing the secret key. 2. The method according to claim 1, wherein the predetermined information for synthesizing the scramble key together with the access passphrase is non-fixed information temporarily generated at the end of use of the secret key. The secret key according to claim 2, wherein the non-fixed information comprises any one of a random number generated by a computer of a communication party, a random input by a keyboard, and an output of a function using time as a factor. Retention management method. 2. The method according to claim 1, wherein the communication partner storing the predetermined information for synthesizing the scramble key is an arbitrary communication partner specified by a user or an information processing device.

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