A codebook is a type of document used for gathering and storing codes. Originally codebooks were often literally books, but today codebook is a byword for the complete record of a series of codes, regardless of physical format.
In cryptography, a codebook is a document used for implementing a code. A codebook contains a lookup table for coding and decoding; each word or phrase has one or more strings which replace it. To decipher messages written in code, corresponding copies of the codebook must be available at either end. The distribution and physical security of codebooks presents a special difficulty in the use of codes, compared to the secret information used in ciphers, the key, which is typically much shorter.
The United States National Security Agency documents sometimes use codebook to refer to block ciphers; compare their use of combiner-type algorithm to refer to stream ciphers.
A codebook is usually made in two parts, one part being for converting plaintext to ciphertext, the other for the opposite purpose. Both are usually organized similar to a standard dictionary, with plaintext words (in the first part) and ciphertext words (in the second part) presented like dictionary headwords.
Ain't it funny how the time slips away
'Cause now I'm leavin' and I wish I could stay
People wonder why they don't get a chance
They wait for music but they don't get to dance
Mmm, well now I know when my work is through
I'm gonna be with you
So goodbye
Is only for now
'Cause I'm comin' back
I swear it somehow
Ain't it funny how we win but we lose
We're given prizes that we don't get to use
People wonder 'bout the things that we've got
It seems so little but we know it's a lot
Now I know when my work is through
I'm gonna be with you, oh yeah
I'm gonna be with you
So goodbye, is only for now
'Cause I'm comin' back, I swear it somehow
Oh, goodbye is only for now
'Cause I'm comin' back, I swear it somehow
Sing it
I'm on the run
So I must go
And I hate to leave
I hope that you know
Oh, goodbye is only for now
'Cause I'm comin' back, I swear it somehow