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"IPG" == IPG Sales <ipgsales@cyberstation.net> writes:
IPG> I find less and less disagreeement with your comments - with IPG> one major exception - for a given message length - say 10 to IPG> the 500th power, a OTP seeded algorithm, a better term would IPG> be to call it an OTP driven algorithm, can produce the exact IPG> same effect as an OTP of that length - that is, the encrypted IPG> text can be any possible message of that length, and it is IPG> not possible to predict in way what the RNG generated stream IPG> is - First, what you describe is commonly called a keyed RNG. Such a system is provably less secure than an OTP, because the number of possible plaintexts from any given ciphertext is limited by the number of possible keys. This makes an exhaustive search of all keys possible, because it is very unlikely that a given ciphertext decrypts to multiple plaintexts that make sense. In contrast, with a OTP there are as many keys as there are possible plaintexts, so any given plaintext can be reached, making it impossible to recognize the correct plaintext. Of course, searching the whole keyspace might be impossible if the number of possible keys is large enough. But there are other ways of attacking a croyptosystem besides trying all possible keys. Your cryptosystem seems to be based on what is called a linear congruential generator in combination whith an RC4-like 8*8 S-box, although somewhat simpler. I don't want to make any claim about the security of the algorithm, but linear congruential generators can't be considered secure for any cryptographic use. Your only chance is that the security of that algorithm does not depend on the generator, but I doubt that. For further reference, go out and buy "Applied Cryptography" by Bruce Schneier. The pseodo-code snipped describing your algorithm, for other people's reference: IPG> Bi=(Bi+Ci MOD Di) Mod 256 Large prime numbers IPG> ENCRYPTEXTi=OTP[Bi] XOR PLAINTEXTi Encryption IPG> OTP[Bi]=ENCRYPTEXTi Makes the OTP Dynamic Andreas -----BEGIN PGP SIGNATURE----- Version: 2.6.2 Comment: Processed by Mailcrypt 3.4, an Emacs/PGP interface iQCVAgUBMSu6OEyjTSyISdw9AQGKIQP+MqE5Scq99kGfLT8CdN3h9abJZNhj9qzm rUFGsnXfdAvyRzfLz6v8FsfLHgnkgu10MG++NABFBz0I+U0iGFi8Zivkd3Ae9/6J qOHqbGjiS4r3QN8IOLDwAW6eO6pF4Z0A/+FqLVR+zB+OZF/7TzUmgWpa8+cLWQkH Hndr5tAVekw= =bY+f -----END PGP SIGNATURE-----