6.2 ECES ~ The Masking Function (continued from the scenario example of Alice and Bob in section 6.1) At this time, Bob and Alice both share the secret value. Because of the difficulty of the ECDLP, Cain, a system perpetrator, cannot determine Alice's private key a nor determine Bob's one-time-use private key b through any intercepted information. This secret value z now becomes the encryption/decryption control for this specific transmission. So far, a secure value z is ready to be used in the encryption process. However, the electronic message is in the form of a bit-string (a long series of 1's and 0's). Suppose that the message M is l bits long. A masking function uses the secret value z to create a second bit-string that is also l bits long. This new bit string, called a mask (denoted by Y) is an non-repeating byte-stream that is specific to the value z. The message can now be encrypted by the control of the mask.
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