Recall that in regular DES, 8 bits of the initial 64-bit key are thrown away, so that the actual encryption only proceeds with the remaining 56 bits and so that an attacker Oscar really only needs those 56 bits to reveal the plaintext. (That is, even though the true keyspace has size 2^64, the keyspace for the keys actually used has size 2^56.) Discuss then whether beginning with a 64-bit key has any merit and if Oscar can simply skip the PC-1 step of DES entirely in carrying out a brute force attack
Recall that in regular DES, 8 bits of the initial 64-bit key are thrown away, so that
the actual encryption only proceeds with the remaining 56 bits and so that an
attacker Oscar really only needs those 56 bits to reveal the plaintext. (That is,
even though the true keyspace has size 2^64, the keyspace for the keys actually
used has size 2^56.) Discuss then whether beginning with a 64-bit key has any
merit and if Oscar can simply skip the PC-1 step of DES entirely in carrying out a
brute force attack.
Data Encryption Standard (DES)
The Data Encryption Standard (DES) is a symmetric-key square code distributed by the National Institute of Standards and Technology (NIST).
DES is an execution of a Feistel Cipher. It utilizes 16 round Feistel structure. The square size is 64-digit. However, key length is 64-cycle, DES has a powerful key length of 56 pieces, since 8 of the 64 pieces of the key are not utilized by the encryption calculation (work as check bits as it were).
DES Features
Highlights: –
- Square size = 64 pieces
- Key size = 56 pieces (in all actuality, 64 pieces, yet 8 are utilized as
- equality check bits for blunder control, see next slide)
- Number of rounds = 16
- 16 go-between keys, each 48 pieces
Step by step
Solved in 3 steps
