Mask generation function: Difference between revisions

Revision as of 14:46, 18 February 2017

Revision as of 14:47, 18 February 2017

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== Applications ==

Mask Generation Functions, as generalizations of hash functions, are useful in all the same cases hash functions are useful. However use of a MGF is desirable in cases where a fixed-size hash would be inadequate. Examples include generating [[Padding (cryptography)|padding]], [[One-time pad|one time pads]] or other forms of [[Symmetric-key_algorithm|symmetric key encryption]], or as the basis of a [[Pseudorandompseudorandom number generator]].

=== Padding Schemes ===

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<pre>

"Salsa20 expandsgenerates athe 256-bitstream key and ain 64-byte (512-bit) nonceblocks. (uniqueEach messageblock number)is intoan

a 270-byte stream. It encrypts a b-byte plaintext by xor’ing the plaintext with

the first b bytes of the stream and discarding the rest of the stream. It decrypts

a b-byte ciphertext by xor’ing the ciphertext with the first b bytes of the stream.

There is no feedback from the plaintext or ciphertext into the stream.

Salsa20 generates the stream in 64-byte (512-bit) blocks. Each block is an

independent hash of the key, the nonce, and a 64-bit block number; there is no

chaining from one block to the next. The Salsa20 output stream can therefore