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Pseudo public key encryptionRelated Patent Categories: Cryptography, Particular Algorithmic Function Encoding, Public KeyPseudo public key encryption description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070189517, Pseudo public key encryption. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to a method and system for a public key encryption, and in particular to a method and system for realizing a pseudo public key cryptosystem at a low cost. BACKGROUND ART [0002] Public key encryption methods, which are especially important among today's encryption techniques, are widely used for encryption, signature and authentication. An algorithm for realizing a public key cryptosystem generally requires a very high cost of calculation. One of practical methods to realize a public key cryptosystem is an RSA cryptography. The RSA cryptography requires an operation of raising a plaintext or a cipher text to the power of the number (an encryption exponent or a decryption exponent) obtained from a value of the Eulerian function of n, which is a product of two large prime numbers and then determining the residue of n, and the cost of this operation is very high. In order to enhance the security of a key, the bit number of n is required to be large. However, the cost of calculation required for RSA cryptography with a large bit number is very high. Though measures such as performing such an operation with dedicated hardware may be taken to seek a high speed, this may impose a development and manufacture cost burden or affect product flexibility. Because of such a situation, the cost of a cryptosystem using a public key is high, and it is difficult to incorporate it in an apparatus which is inexpensively mass-produced. [0003] Also known is elliptic-curve cryptography with a smaller bit number and an equivalent strength in comparison with an RSA cryptography. However, though the cost of operations required for encryption (scalar multiplication of a point on an elliptic curve defined on a finite body, and the like) is lower in comparison with that of modulo exponentiation, the cryptography similarly requires expensive operations, and therefore, it is still difficult to incorporate it in an apparatus which is inexpensively mass-produced. Furthermore, there is also proposed a method for realizing a public key cryptosystem with the use of a secret key cryptosystem and tamper-free hardware. In this method, a receiver encrypts his own secret key with a secret key of a third-party body and publishes it. A sender decrypts it with the secret key of a third-party body, encrypts a message with the obtained secret key of the receiver and sends it. The receiver decrypts it with his own secret key. Because encryption with the secret key of the third-party body, decryption with the secret key of the third-party body and encryption with the secret key of the receiver are performed in temper-proof hardware, security is ensured. In this method, however, the sender and the receiver have to use different hardware, and both of their secret keys are required to use the same hardware. This method is similar to an approach such as an ID-based cryptosystem, in which a public key is distributed not via a certification body, in that an ID is published. In this method, a key generation body generates a user's private key from an unique ID of the user, and anyone can generate the user's public key from the user's ID. This method is convenient with regard to distribution of a public key. However, the nature of the trap-door one-way function in the RSA cryptography and the like is utilized for encryption-decryption of a message, and the cost required for the processing is as high as that of common public key cryptosystems. Patent Document 1 Published Unexamined Patent Application No. 2004-70712 SUMMARY OF THE INVENTION [0004] In a first aspect, the present invention provides methods and systems for realizing a pseudo public key cryptosystem at a low cost. [0005] In another aspect, the present invention provides methods and systems capable of more inexpensively realizing encrypted information communication and code-signed communication with the use of a public key. [0006] In another aspect, the present invention provides methods and systems enabling information processing and communication to be performed with high security maintained, on a terminal such as a mobile terminal on which signature is frequently performed and for which instantaneous processing is required. [0007] In another aspect, the present invention provides methods and systems for realizing a function which requires an expensive operation using pseudo operations. [0008] According to the present invention, a secret key cryptosystem and tamper-proof hardware are used to realize a pseudo public key cryptosystem at a low cost. A trap-door one-way function, which is considered essential for constitution of a public key cryptosystem generally, requires an "expensive" operation. Such a function is substantially realized with the use of tamper-proof hardware. Each user performs communication using equipment provided with hardware having the same capabilities described below. Such hardware retains association between an ID and a key. In response to a request from a user, the hardware issues and stores an ID, and it can perform decryption and generation of a message authentication code (hereinafter referred to as a MAC) with a key associated with the ID. Though this hardware can perform encryption and verification of a MAC with any given ID, it cannot perform decryption and generation of a MAC. A user publishes his ID. When performing encryption, a message sender encrypts a message using the published ID of a message receiver and using hardware having the same capabilities as the receiver's hardware. A person can perform decryption with the ID only by analyzing the mechanism in the hardware. However, the hardware has a capability of destroying itself when such an act is attempted. [0009] Thus, according to the present invention, it is possible to realize encrypted information communication and code-signed communication with the use of a public key at a low cost. By realizing the present invention on a mobile terminal which has recently been used for more and more various purposes, especially on an inexpensive and mass-produced terminal on which signing is frequently performed and from which processing immediacy is required, it is possible to enable information processing and communication requiring high-level security management even on such a terminal. BRIEF DESCRIPTION OF THE DRAWINGS [0010] These, and further, aspects, advantages, and features of the invention will be more apparent from the following detailed description of a preferred embodiment and the appended drawings, wherein: [0011] FIG. 1 is a block diagram of hardware of the present invention; [0012] FIG. 2 is a diagram showing the details of an encryption-authentication section; [0013] FIG. 3 a diagram illustrating sending-receiving protocols of the present invention; [0014] FIG. 4 is a diagram illustrating other sending-receiving protocols of the present invention; [0015] FIG. 5 shows an example of applying the present invention to an ID-based cryptosystem; and [0016] FIG. 6 shows an example of applying the present invention to a mobile phone. DESCRIPTION OF SYMBOLS [0017] 100 . . . System [0018] 101 . . . Encryption-authentication section [0019] 102 . . . Tampering detection section [0020] 201 . . . ID issuance-registration section [0021] 206 . . . ID storage section [0022] 210 . . . Key generation section [0023] 209 . . . Seed storage section [0024] 207 . . . First key acquisition section [0025] 208 . . . Second key acquisition section [0026] 202 . . . Generation section [0027] 204 . . . Verification section [0028] 205 . . . Encryption section [0029] 203 . . . Decryption section [0030] 520 . . . ID storage body DETAILED DESCRIPTION OF THE INVENTION Continue reading about Pseudo public key encryption... Full patent description for Pseudo public key encryption Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Pseudo public key encryption patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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