I'd appreciate greately your enlightened opinions on the following article. (disclaimer : I have no qualification in the Great Science of Cryptology(tm) ; I'm just posting someone's e-mail) About using the electronic signature for protection of commercial information: The analysis of PGP ver.2.0 program. --------------------------------------------------------------------- THE MOSCOW STATE UNIVERSITY named after m.V. Lomonosov ______________________________________________________________ THE MATHEMATICAL CRYPTOGRAPHY PROBLEMS LABORATORY The MSU mathematical cryptography problems laboratory employeers with some addition specialists were executed the preliminary analysis of PGP ver.2.0 program. The preliminary study of working and program source code analysis result in following PGP features and problems: 1. The common character problems - the sequence of random numbers has strong prevalences on bytes (up to 0.05 ... 0.1 on material of 10000 byte) and strong correlation dependence between contiguous bytes; - the program doesn't check it's own integrity, so it can be infected by "virus" which intercept confidential keys and passwords used for their protection and save them onto magnetic carriers; - the program has not optimal exponentiation algorithm in GF(P) field, when P - prime number, which result in low performance; 2. The RSA algorithm realization problems - the prime numbers reception using in this program (R and q in RSA algorithm) permits not less than on two order to reduce the labour-intensiveness of factorization; with 256 bit blocks of data lenght it is possible to execute the cryptanalysis in real time; - before using RSA the program executes compression and block encryption that positively affects on the common stability encryption. 3. The electronic signature problems - for signature calculation the program originally executes hashing of file into number of given length (256, 512 or 1024 bit), but hashing function does not corresponds the ISO recommendations; - when considering the hashing function as the automatic device without output, it is enough simply possible to construct the image of reverse automatic device and with using the blanks in text files (or free fields in some standard formats as in DBF), to compensate the hashing function at changed file to former significance. Thus, it is possible to forge the electronic signature without analysis of RSA algorithm. 4. The block encryption algorithm problems - when executing analysis on plaintext and ciphertext the linear correlation dependences with encryption key were founded (0.01 and more degree); - also the effective method of decreasing security which reduces the order of time necessery to key definition in two times in comparison with exhaustive search of all keys (i.e. algorithm has the labour-intensiveness which is equal the root square from labour-intensiveness of the exhaustive search algorithm) have been found. The conclusions: It is recommended to use encryption with 1024 bit key length. The using of electronic signature is not recommended and requires the additional study. The block encryption algorithm has temporary stability. The hashing function should be reduce in conformity with ISO recommendations. The using of PGP program in actual version is undesired. The MSU mathematical cryptography problems Laboratory Manager Academician Dr. Sidelnikov V.M. ==END