smb (08/04/82)
Does anyone have an implementation of the Rivest-Shamir-Adleman public-key encryption algorithm available? Any responses would be appreciated. (A public-key cryptosystem is one where knowledge of an enciphering algorithm E does not allow one to compute the deciphering algorithm D. Thus, a sender can encrypt some confidential text T with E(T); only the recipient can compute E(D(T))==T. The Rivest-Shamir-Adleman algorithm has the additional interesting property that D(E(T))==T; this can be used to implement "digital signatures", since only the sender can compute E(T), but anyone can apply D to the result and see the original message. This particular algorithm was described in CACM 2/78, and also by Martin Gardener somewhat earlier in Scientific American. The public-key cryptosystem distributed with V7 UNIX is based on a different algorithm, one that cannot -- to my knowledge -- be used for digital signatures.)