Cipher

About: Cipher is a research topic. Over the lifetime, 9409 publications have been published within this topic receiving 110309 citations. The topic is also known as: cypher & cryptographic algorithm.

A provably-secure strongly-randomized cipher

Abstract: Shannon's pessimistic theorem, which states that a cipher can be perfect only when the entropy of the secret key is at least, as great as that of the plaintext, is relativized by the demonstration of a randomized cipher in which the secret key is short but the plaintext can be very long. This cipher is shown to be "perfect with high probability". More precisely, the enemy is unable to obtain any information about the plaintext when a certain security event occurs, and the probability of this event is shown to be arbitrarily close to one unless the enemy performs an infeasible computation. This cipher exploits the existence of a publicly-accessible string of random bits whose length is much greater than that of all the plaintext to be encrypted before the secret key and the randomizer itself are changed. Two modifications of this cipher are discussed that may lead to practical provably-secure ciphers based on either of two assumptions that appear to be novel in cryptography, viz., the (sole) assumption that the enemy's memory capacity (but not his computing power) is restricted and the assumption that an explicit function is, in a specified sense, controllably-difficult to compute, but not necessarily one-way.

The Hill cryptographic system with unknown cipher alphabet but known plaintext

Abstract: The cryptographic equations relating plaintext, ciphertext, and key-matrix elements in the Hill system are nonlinear equations if the cipher alphabet is unknown. In the case where plaintext is known it is possible to reduce these equations to linear equations by the introduction of a larger set of unknowns. These latter equations are analyzed by a method of successive eliminations of unknowns from a series of related row-reduced echelon forms.

Autotest of encryption algorithms in embedded secure encryption devices

Abstract: An internal state machine controller in an integrated circuit containing a cryptographic implementation independently tests and verifies each of the encryption and decryption algorithms and modes within the implementation with minimal processor intervention. The cryptographic implementation automatically generates all input data and exercises all feedback modes independent of the core processor. Eliminating external test vectors results in a device less expensive to manufacture and verify. Since the cryptographic implementation tests are performed independent of the processor, other parts of the integrated circuit may be tested simultaneously with the testing of the cryptographic implementation. The processor loads in a single set of predetermined test vectors and then signals the state machine to start the testing of all the algorithms contained in the module. The output of each algorithm is used as the input of the next algorithm. The encrypted output from each algorithm is then fed back into the algorithms in reverse order and decrypted. At the end of this cycle the data returned should match the original data exactly. This is considered a cycle. The number of cycles is programmable depending on the test requirements and or fault coverage desired. In the preferred embodiment, the cryptographic implementation includes a cryptographic engine having encryption and decryption modes. Output Feedback (OFB), Electronic Codebook (ECB), Cipher Block Chaining (CBC), and Cipher Feedback (CFB) modes are supported in the preferred embodiment of the present invention.

An improved permutation-diffusion type image cipher with a chaotic orbit perturbing mechanism.

Abstract: During the past decades, chaos-based permutation-diffusion type image cipher has been widely investigated to meet the increasing demand for real-time secure image transmission over public networks. However, the existing researches almost exclusively focus on the improvements of the permutation and diffusion methods independently, without consideration of cooperation between the two processes. In this paper, an improved permutation-diffusion type image cipher with a chaotic orbit perturbing mechanism is proposed. In the permutation stage, pixels in the plain image are shuffled with a pixel-swapping mechanism, and the pseudorandom locations are generated by chaotic logistic map iteration. Furthermore, a plain pixel related chaotic orbit perturbing mechanism is introduced. As a result, a tiny change in plain image will be spread out during the confusion process, and hence an effective diffusion effect is introduced. By using a reverse direction diffusion method, the introduced diffusion effect will be further diffused to the whole cipher image within one overall encryption round. Simulation results and extensive cryptanalysis justify that the proposed scheme has a satisfactory security with a low computational complexity, which renders it a good candidate for real-time secure image storage and distribution applications.

Personal identification system

Abstract: A method and apparatus for verifying that the bearer of a card (e.g., credit card, bank card, etc.) is authorized to use the card. The card bears machine-readable indicia of an account number (PAN) and the bearer of the card has memorized a personal identification number (PIN). There is associated with the PAN a check number (PCN) which is derived by (1) generating a first cipher Y1 by encrypting the PAN using the PIN in combination with a secret security number as a key, the bits of which address a data encryption process; (2) generating a second cipher by decrypting the first cipher using the secret security number as a key so that the decryption process is the reverse of the encryption process; and (3) storing the second cipher as the check number PCN in a machine-accessible location, which may be in a separate memory or recorded on the card itself. Verification is accomplished by (a) sensing the PAN from the machine-readable indicia on the card; (b) enciphering the PAN with respect to the data encryption process under control of a key which is a combination (such as by addition) of the PIN and the secret security number to thereby produce a third cipher; (c) sensing the PCN from the machine-accessible location; (d) enciphering the PCN with respect to the data encryption process under control of a key which is the secret security number to thereby produce a fourth cipher; and (e) accepting the card as valid provided the third and fourth ciphers bear a predetermined relationship to each other, such as equality.