ofb.h File Reference

Primitive. More...

#include "ordo/primitives/block_modes.h"

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Functions
ORDO_PUBLIC int	ofb_init (struct OFB_STATE *state, struct BLOCK_STATE *cipher_state, const void *iv, size_t iv_len, int dir, const void *params)
ORDO_PUBLIC void	ofb_update (struct OFB_STATE *state, struct BLOCK_STATE *cipher_state, const void *in, size_t in_len, void *out, size_t *out_len)
ORDO_PUBLIC int	ofb_final (struct OFB_STATE *state, struct BLOCK_STATE *cipher_state, void *out, size_t *out_len)
ORDO_PUBLIC size_t	ofb_query (prim_t cipher, int query, size_t value)
ORDO_PUBLIC size_t	ofb_bsize (void)

Detailed Description

Primitive.

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

Note that the OFB keystream is independent of the plaintext, so a key/iv pair must never be used for more than one message. This also means the block cipher's inverse permutation is never used.

ofb_final() accepts 0 as an argument for out_len since by design the OFB 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 ofb_init	(	struct OFB_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 ofb_update	(	struct OFB_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 ofb_final	(	struct OFB_STATE *	state,
		struct BLOCK_STATE *	cipher_state,
		void *	out,
		size_t *	out_len
	)

See Also

block_mode_final()

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

See Also

block_mode_query()

ORDO_PUBLIC size_t ofb_bsize

(

void

)

Gets the size in bytes of an OFB_STATE.

Returns

The size in bytes of the structure.

Remarks

Binary compatibility layer.