Cryptography – Particular algorithmic function encoding – Public key
Patent
1996-09-23
1998-08-25
Cain, David C.
Cryptography
Particular algorithmic function encoding
Public key
380 46, H04K 100
Patent
active
057990883
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to cryptographic systems and more particularly but not solely to a method and means for realising a computationally secure public-key encryption system and digital signature (authentication) system.
BACKGROUND ART
Data security is an increasingly important aspect in the design of modern communication systems. Encryption systems have been devised in an attempt to scramble or code a message so that to an observer (or "attacker"), the message being communicated appears nonsensical. Many encryption systems have utilised the idea of "keys" with which the message to be communicated is first encoded by the sender and then decoded by the receiver of the message. In this type of conventional encryption system there is the disadvantage that before a message can be decrypted by the intended recipient of the message, the sender of the message must first communicate, to the intended recipient, the decryption key. In addition, any change in the encryption key requires a corresponding change in the decryption key which must then be transmitted to the intended recipient. In the transmission or transportation of keys to the recipient there is always a danger than an observer or attacker will discover the key.
Public-key encryption systems have been developed in order to overcome this problem of the necessity to exchange keys. This type of system was introduced by Diffie and Hellman in 1976 in which each participant in the communication system has two keys, a public key which is made publicly available to all participants in the communication system and a private key which each participant keeps to himself. Each participant's private key is determined (either by choice or random selection) and from the private key the public key is generated. The public key can be thought of as the encryption key (E) while the private key may be thought of as the decryption key (D).
In public key encryption systems, the mathematical relationship which exists between the keys is often a "one-way function." That is, it is arranged that the public key may be relatively easily generated from the private key, however, determining the private key from the public key is computationally infeasible (that is, given an enormous quantity of computational resources, determination of the private key could probably not be effected within a lifetime).
In order for participant A to communicate a message M to a participant B in a public-key encryption system, user A first obtains user B's public key from a publicly available register or file and uses it to encrypt the message M. The ciphertext C is the result of encrypting the message M and is transmitted to user B who then transforms the ciphertext C using his own private key to obtain the message M.
To an observer or attacker wanting to discover the message M and who is aware of the public key and perhaps also has full knowledge of the cryptographic system, the private key (decryption key) must be determined from the known public key. As has been mentioned, the system relies upon the fact that this operation is extremely difficult to carry out. Alternatively, the attacker may have nothing but the intercepted encrypted message and a limited knowledge of the statistical properties of the message language.
An example of a public-key encryption system is disclosed in U.S. Pat. No. 4,405,829 to Rivest et al. The one-way function disclosed makes use of the fact that very large numbers are very hard to factorise. This system, however, has the disadvantage of requiring extensive multiplication of large (for example, 512-bit) integers, which is a very slow process. Another disadvantage of this system is that the encryption method used is completely deterministic, that is, if the same message is later sent to the same recipient, the identical ciphertext is produced, which can enable an attacker or eavesdropper to obtain significant information about message traffic being sent. A further disadvantage is that the system does not permit engineering trade-offs or compromises be
REFERENCES:
patent: 4165444 (1979-08-01), Gordon
LandOfFree
Non-deterministic public key encrypton system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-deterministic public key encrypton system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-deterministic public key encrypton system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-42110