Concepts

Table of Contents

• Stream Ciphers Concept
  • Requirements

Stream Ciphers Concept

A StreamCipher is an object intended to compute non-isomorphic permutations over variable-sized Integral blobs of data.

Requirements

The type X satisfies StreamCipher if

Given

• BlockType, the type named by X::block_type
• KeyScheduleType, the type named by X::key_schedule_type

The following type members must be valid and have their specified effects

Expression	Type	Requirements and Notes
X::block_type	BlockType	BlockType type is a SequenceContainer of type T or std::array<T>
X::word_type	WordType	WordType type satisfies Integral concept
X::key_type	KeyType	KeyType type is a SequenceContainer of type T
X::round_constants_type	RoundConstantsType	RoundConstantsType type satisfies Integral concept

The following static data member definitions must be valid and have their specified effects

Expression	Type	Requirements and Notes
X::word_bits	std::size_t	Integral bits amount in WordType
X::key_bits	std::size_t	Integral bits amount in KeyType
X::block_bits	std::size_t	Integral bits amount in BlockType
X::block_words	std::size_t	Integral amount of WordType values in BlockType
X::rounds	std::size_t	Integral amount of rounds the algorithm does.

The following expressions must be valid and have their specified effects

Expression	Requirements	Return Type
X(key_type)	Constructs stateful StreamCipher object with input key of key_type	StreamCipher
X.encrypt(block_type)	Encrypts a block of data in decoded format specified for particular algorithm. A block can be of a variable size. Should be a non-mutating function depending only on a StreamCipher object inner state of key_type type.	block_type
X.decrypt(block_type)	Decrypts a block of data in encoded format specified for particular algorithm. A block can be of a variable size. Should be a non-mutating function depending only on a StreamCipher object inner state of key_type type.	block_type