lc_chacha20_drng.h File Reference

#include "ext_headers.h"
#include "lc_chacha20.h"

Include dependency graph for lc_chacha20_drng.h:

Go to the source code of this file.

Macros
#define	LC_CC20_DRNG_CTX_ON_STACK(name)
	Allocate stack memory for the ChaCha20 context.

Functions
static void	lc_cc20_drng_zero (struct lc_chacha20_drng_ctx *cc20_ctx)
	Zeroize ChaCha20 DRNG context allocated with either LC_CC20_DRNG_CTX_ON_STACK or lc_cc20_drng_alloc.
int	lc_cc20_drng_alloc (struct lc_chacha20_drng_ctx **cc20_ctx)
	Allocation of a ChaCha20 DRNG context.
void	lc_cc20_drng_zero_free (struct lc_chacha20_drng_ctx *cc20_ctx)
	Zeroize and free ChaCha20 DRNG context.
void	lc_cc20_drng_generate (struct lc_chacha20_drng_ctx *cc20_ctx, uint8_t *outbuf, size_t outbuflen)
	Obtain random numbers.
void	lc_cc20_drng_seed (struct lc_chacha20_drng_ctx *cc20_ctx, const uint8_t *inbuf, size_t inbuflen)
	Reseed the ChaCha20 DRNG.

Macro Definition Documentation

LC_CC20_DRNG_CTX_ON_STACK

#define LC_CC20_DRNG_CTX_ON_STACK

(

name

)

Value:

        _Pragma("GCC diagnostic push")                                              \
                _Pragma("GCC diagnostic ignored \"-Wvla\"") _Pragma(                \
                        "GCC diagnostic ignored \"-Wdeclaration-after-statement\"") \
                        LC_ALIGNED_SYM_BUFFER(name##_ctx_buf, lc_chacha20,          \
                                              LC_CC20_DRNG_CTX_SIZE);               \
        struct lc_chacha20_drng_ctx *name =                                         \
                (struct lc_chacha20_drng_ctx *)name##_ctx_buf;                      \
        LC_CC20_DRNG_SET_CTX(name);                                                 \
        lc_cc20_drng_zero(name);                                                    \
        _Pragma("GCC diagnostic pop")

Allocate stack memory for the ChaCha20 context.

Parameters

[in]

name

Name of the stack variable

Warning

You MUST seed the DRNG!

Definition at line 69 of file lc_chacha20_drng.h.

Function Documentation

lc_cc20_drng_alloc()

int lc_cc20_drng_alloc

(

struct lc_chacha20_drng_ctx **

cc20_ctx

)

Allocation of a ChaCha20 DRNG context.

Parameters

[out]

cc20_ctx

ChaCha20 DRNG context allocated by the function

The cipher handle including its memory is allocated with this function.

The memory is pinned so that the DRNG state cannot be swapped out to disk.

Warning

You MUST seed the DRNG!

Returns

0 upon success; < 0 on error

lc_cc20_drng_generate()

void lc_cc20_drng_generate	(	struct lc_chacha20_drng_ctx *	cc20_ctx,
		uint8_t *	outbuf,
		size_t	outbuflen )

Obtain random numbers.

Parameters

[in]	cc20_ctx	allocated ChaCha20 cipher handle
[out]	outbuf	allocated buffer that is to be filled with random numbers
[in]	outbuflen	length of outbuf indicating the size of the random number byte string to be generated

Generate random numbers and fill the buffer provided by the caller.

After the generation of random numbers, the internal state of the ChaCha20 DRNG is completely re-created using ChaCha20 to provide enhanced backtracking resistance. I.e. if the state of the DRNG becomes known after generation of random numbers, an attacker cannot deduce the already generated random numbers.

lc_cc20_drng_seed()

void lc_cc20_drng_seed	(	struct lc_chacha20_drng_ctx *	cc20_ctx,
		const uint8_t *	inbuf,
		size_t	inbuflen )

Reseed the ChaCha20 DRNG.

Parameters

[in]	cc20_ctx	allocated ChaCha20 cipher handle
[in]	inbuf	buffer with the seed data
[in]	inbuflen	length of inbuf

When calling the function, the DRNG is seeded or reseeded. If it is reseeded, the old state information is mixed into the new state.

lc_cc20_drng_zero()

static void lc_cc20_drng_zero ( struct lc_chacha20_drng_ctx * cc20_ctx )

inlinestatic

Zeroize ChaCha20 DRNG context allocated with either LC_CC20_DRNG_CTX_ON_STACK or lc_cc20_drng_alloc.

Parameters

[in]

cc20_ctx

Hash context to be zeroized

Definition at line 52 of file lc_chacha20_drng.h.

lc_cc20_drng_zero_free()

void lc_cc20_drng_zero_free

(

struct lc_chacha20_drng_ctx *

cc20_ctx

)

Zeroize and free ChaCha20 DRNG context.

Parameters

[in]

cc20_ctx

ChaCha20 DRNG context to be zeroized and freed