Analysis of secret functions with application to computer cryptography

ABSTRACT

In computer cryptography we cannot avoid that data and the corresponding encrypted data can be read by an outside observer. The information contained in these observations may be used to decrypt parts of encrypted data or ultimately to identify the key in the cryptographic transformation. In this paper we have analyzed this situation using the concepts of information theory. The result shows that in most cases it is theoretically possible for an outside observer to identify the key after very few observations. As this must be avoided we have to rely on computational complexity in the process of deriving the key. This is achieved by using one-way functions which are practically impossible to invert.

REFERENCES

• 1: Shannon, Claude, "Communication Theory of Secrecy Systems," Bell Syst. Tech. Journal, Vol. 1949, pp. 656--715.
• 2: "Computer Data Protection," Federal Register, Vol. 40, No. 52, March 17, 1975, pp. 12067--12250.