Showing papers on "Ciphertext published in 1996"

Finding a small root of a univariate modular equation

Abstract: We show how to solve a polynomial equation (mod N) of degree k in a single variable x, as long as there is a solution smaller than N1/k. We give two applications to RSA encryption with exponent 3. First, knowledge of all the ciphertext and 2/3 of the plaintext bits for a single message reveals that message. Second, if messages are padded with truly random padding and then encrypted with an exponent 3, then two encryptions of the same message (with different padding) will reveal the message, as long as the padding is less than 1/9 of the length of N. With several encryptions, another technique can (heuristically) tolerate padding up to about 1/6 of the length of N.

Electronic shopping method, electronic shopping system and document authenticating method relating thereto

Abstract: An electronic shopping method is provided by both an apparatus 10 and an apparatus 30 to hold a key K(A, C) in common, and both the apparatus 30 and an apparatus 40 to hold a key K(B, C) in common. The apparatus 10 transmits a cipher text C1 which is obtained by enciphering a written order P of the products to be purchased using a key K, a cipher text C2 which is obtained by enciphering the key K using the key K(A, C), and authentication information C3 relating to a part P2 of the written order P to the apparatus 30 and the like. The apparatus 40 deciphers the key K on the basis of the cipher text C2, transmits a cipher text C4 which is obtained by enciphering the key K using the key K(B, C) to the apparatus 30. The apparatus 30 deciphers the key K on the basis of the cipher text C4, deciphers the written order P on the basis of the cipher text C1, authenticates the part P2 by referring the authentication information C3, and transmits a fifth cipher text C5 which is obtained by enciphering the authentication information C3 and the part P2 using the key K(B, C) to the apparatus 40. The apparatus 40 deciphers the part P2, and authenticates the part P2 by referring to the authentication information C3.

Automated cryptanalysis of xor plaintext strings

Abstract: In this paper a fully-automated attack on two XORed plaintext strings is implemented using only knowledge of the statistical properties of the plaintext language.

32N +D bit key encryption-decryption system using chaos

Abstract: A cryptographic method and system based on chaos theory is provided. Unique random 64-bit binary strings generated from an iterative chaotic equation are used as logic and arithmetic operands during encryption/decryption. The random 64-bit binary strings are generated based on 4 initializer values that produce thousands of iterated values from the chaotic equation zt+1 = zt2 + c, where z and c are complex numbers. The 64-bit random numbers are translated into two 32-bit keys so that each 32 bits of message are encrypted/decrypted, using a bitwise logic operator such as an exclusive-or, with a unique 32-bit key for the length of the message file. For additional security, a combination of logic and arithmetic operators are used on the 32-bit keys and the 32-bit blocks of message text to produce 32N-bit blocks of ciphertext, where N = 2?r? and r ≤ 2. For any set of 4 initializer values, the lifetime, n, is the number of iterations of the equation zt+1 = zt?2? + c before divergence of the output to infinity, and the number of unique 32-bit keys is 4n, where n can be over 300,000 for a multitude of initializer values.

Cryptographic apparatus with double feedforward hash function

Abstract: Apparatus is provided for authenticating information using a double feedforward hash function to provide complementarity in the implementation of an encryption algorithm. A cryptographic processor has a first input for receiving plaintext, a second input for receiving a key and an output for outputting ciphertext generated by cryptographically processing the plaintext and key. A first circuit element is responsive to the ciphertext and plaintext for outputting a first ciphertext derivative. A second circuit element is responsive to at least a portion of the first ciphertext derivative and the key for outputting a second ciphertext derivative. The first and second circuit elements can be XOR gates. Alternatively, these elements can be provided using lookup tables. Subsequent cryptographic processor stages can be provided having a first input for receiving second plaintext, a second input for receiving the second ciphertext derivative as a key, and an output for outputting second ciphertext generated by cryptographically processing the second plaintext and the second ciphertext derivative. In an illustrated embodiment, the cryptographic processor is a DES processor.

Method for data encryption/decryption using cipher block chaining (CBC) and message authetication codes (MAC)

Abstract: A method for encrypting a plaintext string into ciphertext begins by cipher block chaining (CBC) (70) the plaintext using a first key and a null initialization vector to generate a CBC message authentication code (MAC) whose length is equal to the block length. The plaintext string is then cipher block chained (72) again, now using a second key and the CBC-MAC as the initialization vector, to generate an enciphered string. The CBC-MAC and a prefix of the enciphered string comprising all of the enciphered string except the last block are then combined (74) to create the ciphertext. The described mode of operation is length-preserving, yet has the property that related plaintexts give rise to unrelated ciphertexts.

Certification method, communication method and information processing device

Abstract: PROBLEM TO BE SOLVED: To perform the certification mutually, by enciphering a clear text mutually received, to transmit the same to a device which has transmitted the clear text, and comparing the clear text obtained by decoding the received cipher text, with the clear text which has been transmitted first. SOLUTION: A reader writer(R/W) 1 enciphers random numbers RA to a cipher C1 with a key KLB, and an IC card 2 encodes the cipher C1 to a clear text M1 with the key KB. The IC card 2 enciphers the clear text M1 to a cipher C2 with a key KA, the random number RB is enciphered to a cipher C3 with the key KA, and R/W 1 encodes the cipher C2 to the clear text M2 with the key KA. And the R/W 1 certifies the IC card 2 when the clear text M2 and the random number RA are judged to be same as each other. In the next, R/W 1 encodes the cipher C3 to a clear text M3 with the key KA, the clear text M3 is encoded to a cipher C4 with the key KB, and the IC card 2 encodes the cipher C4 to the clear text M4 with the key KB. And the IC card 2 certifies R/W1, when the clear text M4 and the random number RB are judged to be same as each other.

Security of private-key encryption based on array codes

Abstract: A chosen plaintext attack is presented for constructing all the private keys of cryptosystems based on array codes.

Encryption device, decode device and method therefor

Abstract: PROBLEM TO BE SOLVED: To make it hard to illegally decode a secret key by updating a temporary key as a secret key in every preprocessing or postprocessing in encryption and decode processing. SOLUTION: A control processing part 7 reads symmetrical cipher algorithm F from 1st nonvolatile memory 1, makes the algorithm F process a secret key SK and a random number which are stored in volatile memory 9 and stores the information generated from this processed result as a key for temporary cipher processing, i.e., a temporary key in the memory 9. Next, the part 7 makes the algorithm F process a clear text and the temporary key which are stored in the memory 9 and stores this processed result as a cipher text in the memory 9. When the cipher text is created in this way, the part 7 reads the temporary key stored in the memory 9, rewrites and updates a secret key which is stored in 2nd nonvolatile memory 3 with this temporary key and prepares for the next encryption processing.

Method and apparatus for encryption by using two keys

Abstract: PROBLEM TO BE SOLVED: To provide a deterministic and history-free plaintext string encryption method. SOLUTION: An encryption method, by which a plaintext string is encrypted into a ciphertext, is started when the plaintext is encryption block chained (CBC) by using the first key and an empty initial setting vector and a CBC message check code (MAC) with a length equal to the block length is generated. Then, the plaintext string is encryption block chained again by using the second key and a CBC-MAC as an initial setting vector, and an encryption string is formed. Prefixes of the encryption string including all the blocks excepting the CBC-MAC and the final block are combined together, and the cihertext is generated. In this process, an encryption using mode provided with a length maintenance property is also provided with a such a property as makes the related plaintext generate an unrelated ciphertext.

Ciphering device, deciphering device, ciphering and deciphering device and cipher system

Abstract: PURPOSE: To provide a ciphering device and a cipher system particularly excellent in the deciphering speed as compared with RSA ciphers in use. CONSTITUTION: This device is provided with a key generation means 14 which generates primes p and q and at the time of computation with dp and dq satisfying dp =(1/e)mod(p-1), dq =(1/e)mod(q-1), where an integer e is mutually prime with the least common multiple of the product n=pq, (p-1) and (q-1), sets the product n and an integer e to be public keys and sets the primes p, q and dp , dq to be secret keys. In addition the device is provided with a ciphering calculation means which makes an integer pair of inputted plain texts correspond to a point on a cubic curve, determines a point obtained by e-folding the point by the use of the public keys by arithmetic on the cubic curve, and outputs arithmetic results as a cipher text, and a deciphering arithmetic means which subjects the integer pair of the inputted cipher text to homomorphic transformation, then raises the result to the dp -th power under a divisor p and dq -th power under a divisor q, and synthesizes them by the use of the Chinese remainder theorem to output a plain text.

Encoding device, decoding device and ic card

Abstract: PROBLEM TO BE SOLVED: To provide an encoding device, a decoding device and an IC card that can establish security of high reliability SOLUTION: In an encoding device, a decoding device, a random number determining part 11 determines a random number (a first secret key) C on the basis of random number selecting information using a random number generating method selected by a random number generating method selecting part 10, while an algorithm selecting part 13 selects secret key cipher system algorithm E on the basis of algorithm selecting information In addition, a secret key encoding part 12 converts encoded object data B into secret key cipher text by a random number C and algorithm E, and an open key encoding part 15 converts the random number C and algorithm selecting information into open key cipher text A coalesced cipher text preparing part 14 then prepares the coalesced cipher text of the secret key cipher text and open key cipher text

Digital information privacy system

Abstract: A system for determining a maximum length digital sequence is constructed by selecting a Mersenne Prime integer and a primitive polynomial having an ORDER equal to the Mersenne Prime integer. An arbitrarily selected mask m is either provided to the transmitter and receiver, or constructed, at either, or both. The mask is used to create a decimated M sequence, and work backwards to define a recursion rule vector r which is associated with another primitive polynomial corresponding to the decimated M sequence. This recursion rule vector r is used to create a new feedback shift register which produces a maximum length sequence. An initialization vector i is provided to the transmitter and receiver and used as an initial load of the shift register. A selected stage of this register is exclusive-ORed ("XORed") with each bit of a plaintext message to be sent to result in cipher text. At the receiver, the same process is performed with the same mask m, and initialization vector i, to create the same recursion rule vector r, and shift register. The same stage of this shift register is then XORed with the received ciphertext message to result in the original plaintext message.

Primes and Secret Codes

Abstract: Humankind’s desire to conceal sensitive messages is only surpassed by its ingenuity in devising the means to do so. Properly speaking, the secret to be sent is called a message (also called the plaintext). The sender alters this message by enciphering it or creating a ciphertext which cannot be read by any unauthorized person (an intruder or spy) who may intercept it. This cipher is transmitted to the receiver who deciphers the ciphertext, changing it back into the original message. This whole science is called cryptography. An unauthorized person who wishes to understand the message must break the cipher. Breaking ciphers is the science of cryptanalysis.