摘要:
In a system for de-/encoding data using (de)coding devices at either end of a transmission channel, the data sometimes comprise additional synchronisation information which is used to reduce the effect of faults in the transmission channel. If this synchronisation information is not already present, it is impossible in certain cases to add such information. The invention provides a system which, regardless of the presence of additional synchronisation information, is able to reduce the effect of faults. For this purpose, each (de)coding device is provided with means for comparing sequences of encoded data with at least one predetermined code word and for setting the associated coding device to a reset state in the event of equality. Because the predetermined code word repeats statistically in the encoded data, a fault adversely affects the decoding for not more than one time interval.
摘要:
The invention provides a device (1) for encrypting or decrypting data packets, comprising storage means (14) for temporarily storing data packets, identification means (15) for identifying data packets, processing means (11, 12, 13) for cryptographically processing data packets, and memory means (16) for storing cryptographic information. The processing means (11, 12, 13) comprise, according to the invention, a first (11) and a second (12) cryptographic element, the first cryptographic element (11) being designed for generating, on the basis of a first starting value, processing data for cryptographically processing a data packet, and the second cryptographic element (12) being designed for generating, on the basis of a second starting value, the first starting value. In addition, the processing means (11, 12, 13) according to the invention are designed for forming, on the basis of a cryptographically processed data packet, the second starting value, thereby ensuring the synchronization between corresponding encrypting and decrypting devices.
摘要:
Two novel cryptographic modes are presented in which a perturbation of the encrypted character stream (b) always results in a permanent perturbation of the output stream (c) of the decryption device. Two options are presented: feedback of the encryption character stream (d and e, respectively) and simultaneously feeding back, in accordance with a function f, (option 1) the encrypted character stream (b) or (option 2) the original character stream (a) to the encryption side and, respectively, the output character stream (c) to the decryption side.
摘要:
The invention relates to an encipher algorithm on the basis of a secret key, in which use is made of a substitution function, S(n,k), known as S-box, with which a series of n symbols (for example bits) can be replaced by a series of k symbols. On the basis of the secret key, an arbitrary S-box is always generated in order to avoid the use of preselected S-boxes. Such a generation can generally take place in such a way that the substitution result almost certainly does have non-linearity, but not, that it moreover has good statistical properties. These properties will be obtained, either dynamically (figure 1), if the bits of a temporary substitution result (contents of register 3) are moreover combined, via a modulo-2 adder 5, with the bits of a series with a good statistical distribution (contents of register 4) to the proper substitution result (contents of register 6), or statically (figure 2), if a series of n bits (contents of register 2′) to be substituted is combined with the k bits of a series with a good statistical distribution (contents of register 4′) to a series of n + k bits, which is subsequently substituted by means of a substitution function S{n+k,k} of S-box 1′. The advantages are that a preselection of S-boxes with good statistical and non-linear properties can be dispensed with, and that the S-boxes always change and consequently are not known, which will benefit the strength of the encipher algorithm.