cfb.h File Reference

Primitive. More...

#include "ordo/primitives/block_modes.h"

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Functions
ORDO_PUBLIC int	cfb_init (struct CFB_STATE *state, struct BLOCK_STATE *cipher_state, const void *iv, size_t iv_len, int dir, const void *params)
ORDO_PUBLIC void	cfb_update (struct CFB_STATE *state, struct BLOCK_STATE *cipher_state, const void *in, size_t in_len, void *out, size_t *out_len)
ORDO_PUBLIC int	cfb_final (struct CFB_STATE *state, struct BLOCK_STATE *cipher_state, void *out, size_t *out_len)
ORDO_PUBLIC size_t	cfb_query (prim_t cipher, int query, size_t value)
ORDO_PUBLIC size_t	cfb_bsize (void)

Detailed Description

Primitive.

The CFB mode generates a keystream by repeatedly encrypting an initialization vector and mixing in the plaintext, effectively turning a block cipher into a stream cipher. As such, CFB mode requires no padding, and the ciphertext size will always be equal to the plaintext size.

Note that the CFB keystream depends on the plaintext fed into it, as opposed to OFB mode. This also means the block cipher's inverse permutation is never used.

cfb_final() accepts 0 as an argument for out_len since by design the CFB 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 cfb_init	(	struct CFB_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 cfb_update	(	struct CFB_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 cfb_final	(	struct CFB_STATE *	state,
		struct BLOCK_STATE *	cipher_state,
		void *	out,
		size_t *	out_len
	)

See Also

block_mode_final()

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

See Also

block_mode_query()

ORDO_PUBLIC size_t cfb_bsize

(

void

)

Gets the size in bytes of a CFB_STATE.

Returns

The size in bytes of the structure.

Remarks

Binary compatibility layer.