The document discusses cryptographic algorithms and keys. It describes the RC4 algorithm which uses a key stream to encrypt plaintext into ciphertext. It involves initializing a state array S with permutations, then generating a pseudo-random key stream by swapping array bytes based on the key and indices i and j. The key stream is then combined with plaintext to produce ciphertext. The document also mentions SSL and provides several references on RC4, WEP attacks, and cryptographic algorithm breakdowns.