stream.md

Stream ciphers

#include <maid/stream.h>

Internal Interface

struct maid_stream_def

Type that defines a stream cipher algorithm

External Interface

maid_stream

Opaque type that contains the state of a stream cipher

maid_stream *maid_stream_new(struct maid_stream_def def, const u8 *restrict key, const u8 *restrict nonce, u64 counter)

Creates a stream cipher instance

Parameters

name	description
def	Algorithm definition
key	Algorithm-dependent
nonce	Algorithm-dependent
counter	Algorithm-dependent

Return value

case	description
Success	maid_stream instance
Failure	NULL

maid_stream *maid_stream_del(maid_stream *st)

Deletes a stream cipher instance

Parameters

name	description
st	maid_stream instance

Return value

case	description
Always	NULL

void maid_stream_renew(maid_stream *st, const u8 *restrict key, const u8 *restrict nonce, u64 counter)

Recreates a stream cipher instance

Parameters

name	description
st	maid_stream instance
key	Algorithm-dependent
nonce	Algorithm-dependent
counter	Algorithm-dependent

void maid_stream_xor(maid_stream *st, u8 *buffer, size_t size)

Generates keystream, and applies it with a xor operation

Parameters

name	description
st	maid_stream instance
buffer	Memory to be ciphered
size	Size of the operation

External Algorithms

const struct maid_stream_def maid_chacha20

Chacha20 stream cipher (IETF version)

Parameters

name	description
key	256-bit key
nonce	96-bit nonce
counter	0 to 2^32

Example Code

#include <stdio.h>
#include <stdlib.h>

#include <maid/stream.h>

int main(void)
{
    u8 key[32] = {0};
    u8 iv [16] = {0};

    maid_stream *st = maid_stream_new(maid_chacha20, key, iv, 0);

    u8 data[64] = {0};
    if (st)
        maid_stream_xor(st, data, sizeof(data));

    maid_stream_del(st);

    for (size_t i = 0; i < sizeof(data); i++)
        printf("%02x", data[i]);
    printf("\n");

    return EXIT_SUCCESS;
}

Without installation:

cc -static -Iinclude example.c -Lbuild -lmaid

With installation:

cc example.c -lmaid