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What are the Properties of Data Encryption Standard?
DES is a block cipher. The encryption procedure is create of two permutations (Pboxes) that it can be defined initial and final permutations, and 16 Feistel rounds. Each round need a different 48-bit round key created from the cipher key according to a pre-represented algorithm. The DES function uses a 48-bit key to the rightmost 32 bits (RI−1) to create a 32-bit output.
There are two properties of DES which are as follows −
- Avalanche Effect
Avalanche effect defines a small change in the plaintext (or key) should make an important change in the ciphertext. It can change in one bit of plaintext creates change in some bits of the ciphertext
DES has been proved to be powerful regarding this property.
Avalanche effect is the number of cipher text bits transforming regarding bit by bit in plain text and key values.
The advantage of Avalanche effect can be made accessible in securing embedded software wherever DES and AES algorithms are used. The attackers are attempting a lot to smuggle the data saved in the databases.
If the change were small, it decrease the size of the plaintext or key area to be searched.
This defines that there should not be any resemblance between two ciphertexts obtained by using two neighboring keys for encrypting the similar plaintext, therefore this can lead to large decline of the keyspace inspection by the cryptanalyst.
An encryption approach has a good avalanche effect when a change in one bit of input outcomes in a random change of about half of the output bit.
In Avalanche effect, it is an essential characteristic for encryption algorithm. This property can be view when transforming some bit in plaintext and then watching the avalanche change in the result of the bits in the cipher text.
- Completeness
Completeness effect defines that each bit of the ciphertext required to base on some bits on the plaintext. The diffusion and confusion developed by Dboxes and S-boxes in DES, show a very strong completeness effect.
The completeness feature tightness the avalanche concept even more.
It needed that change in the ciphertext is consistently distributed for each changed bit of the input plaintext or the key.
In specific, changing any given input bit should create a change in a definite output bit at some point in the transformation.
Completeness needed that this relationship appears at least once for each sequence of input bit and output bit.
In other words, completeness defines that the avalanche effect spans across all group of bits in the plaintext and ciphertext almost consistently.
This effect is developed by diffusion and confusion created by P-boxes and Sboxes. DES display very strong completeness effect.
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