ChaCha20Aligned Class Reference

ChaCha20 cipher that only operates on multiples of 64 bytes. More...

#include <chacha20.h>

Public Types
using	Nonce96 = std::pair< uint32_t, uint64_t >
	Type for 96-bit nonces used by the Set function below. More...

Public Member Functions
	ChaCha20Aligned () noexcept=delete
	For safety, disallow initialization without key. More...
	ChaCha20Aligned (std::span< const std::byte > key) noexcept
	Initialize a cipher with specified 32-byte key. More...
	~ChaCha20Aligned ()
	Destructor to clean up private memory. More...
void	SetKey (std::span< const std::byte > key) noexcept
	Set 32-byte key, and seek to nonce 0 and block position 0. More...
void	Seek (Nonce96 nonce, uint32_t block_counter) noexcept
	Set the 96-bit nonce and 32-bit block counter. More...
void	Keystream (std::span< std::byte > out) noexcept
	outputs the keystream into out, whose length must be a multiple of BLOCKLEN. More...
void	Crypt (std::span< const std::byte > input, std::span< std::byte > output) noexcept
	en/deciphers the message <input> and write the result into <output> More...

Static Public Attributes
static constexpr unsigned	KEYLEN {32}
	Expected key length in constructor and SetKey. More...
static constexpr unsigned	BLOCKLEN {64}
	Block size (inputs/outputs to Keystream / Crypt should be multiples of this). More...

Private Attributes
uint32_t	input [12]

Detailed Description

ChaCha20 cipher that only operates on multiples of 64 bytes.

Definition at line 24 of file chacha20.h.

Member Typedef Documentation

Nonce96

using ChaCha20Aligned::Nonce96 = std::pair<uint32_t, uint64_t>

Type for 96-bit nonces used by the Set function below.

The first field corresponds to the LE32-encoded first 4 bytes of the nonce, also referred to as the '32-bit fixed-common part' in Example 2.8.2 of RFC8439.

The second field corresponds to the LE64-encoded last 8 bytes of the nonce.

Definition at line 56 of file chacha20.h.

Constructor & Destructor Documentation

ChaCha20Aligned() [1/2]

ChaCha20Aligned::ChaCha20Aligned ( )

deletenoexcept

For safety, disallow initialization without key.

ChaCha20Aligned() [2/2]

ChaCha20Aligned::ChaCha20Aligned ( std::span< const std::byte >  key )

noexcept

Initialize a cipher with specified 32-byte key.

Definition at line 46 of file chacha20.cpp.

~ChaCha20Aligned()

ChaCha20Aligned::~ChaCha20Aligned

(

)

Destructor to clean up private memory.

Definition at line 41 of file chacha20.cpp.

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Member Function Documentation

Crypt()

void ChaCha20Aligned::Crypt ( std::span< const std::byte >  input, std::span< std::byte >  output  )

inlinenoexcept

en/deciphers the message <input> and write the result into <output>

The size of input and output must be equal, and be a multiple of BLOCKLEN.

Definition at line 160 of file chacha20.cpp.

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Keystream()

void ChaCha20Aligned::Keystream ( std::span< std::byte >  out )

inlinenoexcept

outputs the keystream into out, whose length must be a multiple of BLOCKLEN.

Definition at line 59 of file chacha20.cpp.

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Seek()

void ChaCha20Aligned::Seek ( Nonce96  nonce, uint32_t  block_counter  )

noexcept

Set the 96-bit nonce and 32-bit block counter.

Block_counter selects a position to seek to (to byte BLOCKLEN*block_counter). After 256 GiB, the block counter overflows, and nonce.first is incremented.

Definition at line 51 of file chacha20.cpp.

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SetKey()

void ChaCha20Aligned::SetKey ( std::span< const std::byte >  key )

noexcept

Set 32-byte key, and seek to nonce 0 and block position 0.

Definition at line 24 of file chacha20.cpp.

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Member Data Documentation

BLOCKLEN

constexpr unsigned ChaCha20Aligned::BLOCKLEN {64}

staticconstexpr

Block size (inputs/outputs to Keystream / Crypt should be multiples of this).

Definition at line 34 of file chacha20.h.

input

uint32_t ChaCha20Aligned::input[12]

private

Definition at line 27 of file chacha20.h.

KEYLEN

constexpr unsigned ChaCha20Aligned::KEYLEN {32}

staticconstexpr

Expected key length in constructor and SetKey.

Definition at line 31 of file chacha20.h.

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The documentation for this class was generated from the following files:

• src/crypto/chacha20.h
• src/crypto/chacha20.cpp