Construction Details
Let be the round function and let be the sub-keys for the rounds respectively.
Then the basic operation is as follows:
Split the plaintext block into two equal pieces, (, )
For each round, compute
- .
Then the ciphertext is .
Decryption of a ciphertext is accomplished by computing for
- .
Then is the plaintext again.
One advantage of the Feistel model compared to a substitution-permutation network is that the round function does not have to be invertible.
The diagram illustrates both encryption and decryption. Note the reversal of the subkey order for decryption; this is the only difference between encryption and decryption.
Read more about this topic: Feistel Cipher
Famous quotes containing the words construction and/or details:
“There’s no art
To find the mind’s construction in the face.”
—William Shakespeare (1564–1616)
“There was a time when the average reader read a novel simply for the moral he could get out of it, and however naïve that may have been, it was a good deal less naïve than some of the limited objectives he has now. Today novels are considered to be entirely concerned with the social or economic or psychological forces that they will by necessity exhibit, or with those details of daily life that are for the good novelist only means to some deeper end.”
—Flannery O’Connor (1925–1964)