A cipher system is disclosed in which each character of a plaintext alphabet has associated with it a randomly distributed collection of integers of a given length. This collection of integers is secretly shared by a sender and receiver pair. The plaintext characters of a message are sequentially coded by pseudo-randomly selecting representatives from the integer collections corresponding to the plaintext characters. To this sequence of concatenated integers, regarded as a single integer, is added a pseudo-random integer of length equal to that of the coded-for-message integer string. This pseudo-random integer is generated by a pseudo-random number generator (The receiver has a corresponding generator.), the output of which is initialized by a "seed" integer concealed in the cryptogram. The summed pseudo-random integer plus the coding integer string is transmitted as the body of the cryptogram. To decrypt, the receiver subtracts the pseudo-random integer from the transmitted integer, breaks up the remaining integer into the blocks numerically coding the plaintext characters and retrieves the plaintext characters of the message. Provision is made for further obscuring the cryptogram integer.