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Stream Ciphers
The Caesar cipher, other substitution ciphers, and the "one-time pad" are all examples of stream ciphers.
A stream cipher is a symmetric key cipher where plaintext digits are combined with a key stream. In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream.
Assignments
We've been asked to update our "One Time Pad". For performance reasons, we'll now be reading and writing the data using Go channels. This will allow us to encrypt the data as it's read in from an external database. Rather than storing the entire message in memory (which could be many Gigabytes) and then decrypting it all at once, this new crypt function can do it one character at a time.
func crypt(textCh, keyCh <-chan byte, result chan<- byte)
Read one byte at a time from the textCh and keyCh channels. Perform an XOR operation on the two bytes and write the result to the result channel. Stop once either channel is closed.
Be sure to close the result channel when you're done writing to it.