ctr.h File Reference

Primitive. More...

#include "ordo/primitives/block_modes.h"

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Functions
ORDO_PUBLIC int	ctr_init (struct CTR_STATE *state, struct BLOCK_STATE *cipher_state, const void *iv, size_t iv_len, int dir, const void *params)
ORDO_PUBLIC void	ctr_update (struct CTR_STATE *state, struct BLOCK_STATE *cipher_state, const void *in, size_t in_len, void *out, size_t *out_len)
ORDO_PUBLIC int	ctr_final (struct CTR_STATE *state, struct BLOCK_STATE *cipher_state, void *out, size_t *out_len)
ORDO_PUBLIC size_t	ctr_query (prim_t cipher, int query, size_t value)
ORDO_PUBLIC size_t	ctr_bsize (void)

Detailed Description

Primitive.

The CTR mode generates a keystream by repeatedly encrypting a counter starting from some initialization vector, effectively turning a block cipher into a stream cipher. As such, CTR mode requires no padding, and outlen will always be equal to inlen.

Note that the CTR keystream is independent of the plaintext, and is also spatially coherent (using a given initialization vector on a len-byte message will "use up" len bytes of the keystream) so care must be taken to avoid reusing the initialization vector in an insecure way. This also means the block cipher's inverse permutation is never used.

ctr_final() accepts 0 as an argument for out_len since by design the CTR mode of operation does not produce any final data. However, if a valid pointer is passed, its value will be set to zero as expected.

Function Documentation

ORDO_PUBLIC int ctr_init	(	struct CTR_STATE *	state,
		struct BLOCK_STATE *	cipher_state,
		const void *	iv,
		size_t	iv_len,
		int	dir,
		const void *	params
	)

See Also

block_mode_init()

ORDO_PUBLIC void ctr_update	(	struct CTR_STATE *	state,
		struct BLOCK_STATE *	cipher_state,
		const void *	in,
		size_t	in_len,
		void *	out,
		size_t *	out_len
	)

See Also

block_mode_update()

ORDO_PUBLIC int ctr_final	(	struct CTR_STATE *	state,
		struct BLOCK_STATE *	cipher_state,
		void *	out,
		size_t *	out_len
	)

See Also

block_mode_final()

ORDO_PUBLIC size_t ctr_query	(	prim_t	cipher,
		int	query,
		size_t	value
	)

See Also

block_mode_query()

ORDO_PUBLIC size_t ctr_bsize

(

void

)

Gets the size in bytes of a CTR_STATE.

Returns

The size in bytes of the structure.

Remarks

Binary compatibility layer.