What is the key size of Data Encryption Standard algorithm in cryptography ?

What is the key size of Data Encryption Standard algorithm in cryptography ? Correct Answer 56 bit

The Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data.

Data encryption standard (DES) is a block cipher that encrypts data in blocks of size 64 bits each. That is 64 bits of plain text goes input to the DES which produces 64 bit of cipher text. Key length is 56 bits.

DES is insecure due to the relatively short 56-bit key size.

Important Points

Broad level steps of DES are:

• In first step, 64 – bit plain text block is handed over to initial permutation.
• Next , initial permutation (IP) produces two halves of permuted block, say left plain text and right plain text
• Now, each LPT and RPT go through 16 rounds of encryption process each with its own key.
• At the end, LPT and RPT are re-joined and a final permutation is performed on combined block.

Each of the 16 rounds, in turn consists of these steps:

During expansion permutation, it goes to S- box substitution after doing XOR of 48 bit key with 48 bit right plain text. S- Box produces the 32-bit output using substitution technique. Then a straight permutation is done. These 32 bits are permuted using P- box.

Advanced Encryption Standard (AES) keys are symmetric keys that can be three different key lengths (128, 192, or 256 bits).