RFC 2268 (rfc2268) - Page 2 of 11

A Description of the RC2(r) Encryption Algorithm

RFC 2268              RC2(r) Encryption Algorithm             March 1998


     Encryption. This takes a 64-bit input quantity stored in words
     R[0], ..., R[3] and encrypts it "in place" (the result is left in
     R[0], ..., R[3]).

     Decryption. The inverse operation to encryption.

2. Key expansion

   Since we will be dealing with eight-bit byte operations as well as
   16-bit word operations, we will use two alternative notations

   for referring to the key buffer:

        For word operations, we will refer to the positions of the
             buffer as K[0], ..., K[63]; each K[i] is a 16-bit word.

        For byte operations,  we will refer to the key buffer as
             L[0], ..., L[127]; each L[i] is an eight-bit byte.

   These are alternative views of the same data buffer. At all times it
   will be true that

                       K[i] = L[2*i] + 256*L[2*i+1].

   (Note that the low-order byte of each K word is given before the
   high-order byte.)

   We will assume that exactly T bytes of key are supplied, for some T
   in the range 1