/*
 * Interface declarations for Skein hashing.
 * Source code author: Doug Whiting, 2008.
 * This algorithm and source code is released to the public domain.
 *
 * The following compile-time switches may be defined to control some
 * tradeoffs between speed, code size, error checking, and security.
 *
 * The "default" note explains what happens when the switch is not defined.
 *
 *  SKEIN_DEBUG            -- make callouts from inside Skein code
 *                            to examine/display intermediate values.
 *                            [default: no callouts (no overhead)]
 *
 *  SKEIN_ERR_CHECK        -- how error checking is handled inside Skein
 *                            code. If not defined, most error checking
 *                            is disabled (for performance). Otherwise,
 *                            the switch value is interpreted as:
 *                                0: use assert()      to flag errors
 *                                1: return SKEIN_FAIL to flag errors
 */
/* Copyright 2013 Doug Whiting. This code is released to the public domain. */
#ifndef _SYS_SKEIN_H_
#define _SYS_SKEIN_H_

#include <sys/types.h>          /* get size_t definition */

#ifdef  __cplusplus
extern "C" {
#endif

enum {
        SKEIN_SUCCESS = 0,      /* return codes from Skein calls */
        SKEIN_FAIL = 1,
        SKEIN_BAD_HASHLEN = 2
};

#define SKEIN_MODIFIER_WORDS    (2)     /* number of modifier (tweak) words */

#define SKEIN_256_STATE_WORDS   (4)
#define SKEIN_512_STATE_WORDS   (8)
#define SKEIN1024_STATE_WORDS   (16)
#define SKEIN_MAX_STATE_WORDS   (16)

#define SKEIN_256_STATE_BYTES   (8 * SKEIN_256_STATE_WORDS)
#define SKEIN_512_STATE_BYTES   (8 * SKEIN_512_STATE_WORDS)
#define SKEIN1024_STATE_BYTES   (8 * SKEIN1024_STATE_WORDS)

#define SKEIN_256_STATE_BITS    (64 * SKEIN_256_STATE_WORDS)
#define SKEIN_512_STATE_BITS    (64 * SKEIN_512_STATE_WORDS)
#define SKEIN1024_STATE_BITS    (64 * SKEIN1024_STATE_WORDS)

#define SKEIN_256_BLOCK_BYTES   (8 * SKEIN_256_STATE_WORDS)
#define SKEIN_512_BLOCK_BYTES   (8 * SKEIN_512_STATE_WORDS)
#define SKEIN1024_BLOCK_BYTES   (8 * SKEIN1024_STATE_WORDS)

typedef struct {
        size_t hashBitLen;      /* size of hash result, in bits */
        size_t bCnt;            /* current byte count in buffer b[] */
        /* tweak words: T[0]=byte cnt, T[1]=flags */
        uint64_t T[SKEIN_MODIFIER_WORDS];
} Skein_Ctxt_Hdr_t;

typedef struct {                /*  256-bit Skein hash context structure */
        Skein_Ctxt_Hdr_t h;     /* common header context variables */
        uint64_t X[SKEIN_256_STATE_WORDS];      /* chaining variables */
        /* partial block buffer (8-byte aligned) */
        uint8_t b[SKEIN_256_BLOCK_BYTES];
} Skein_256_Ctxt_t;

typedef struct {                /*  512-bit Skein hash context structure */
        Skein_Ctxt_Hdr_t h;     /* common header context variables */
        uint64_t X[SKEIN_512_STATE_WORDS];      /* chaining variables */
        /* partial block buffer (8-byte aligned) */
        uint8_t b[SKEIN_512_BLOCK_BYTES];
} Skein_512_Ctxt_t;

typedef struct {                /* 1024-bit Skein hash context structure */
        Skein_Ctxt_Hdr_t h;     /* common header context variables */
        uint64_t X[SKEIN1024_STATE_WORDS];      /* chaining variables */
        /* partial block buffer (8-byte aligned) */
        uint8_t b[SKEIN1024_BLOCK_BYTES];
} Skein1024_Ctxt_t;

/*   Skein APIs for (incremental) "straight hashing" */
int Skein_256_Init(Skein_256_Ctxt_t *ctx, size_t hashBitLen);
int Skein_512_Init(Skein_512_Ctxt_t *ctx, size_t hashBitLen);
int Skein1024_Init(Skein1024_Ctxt_t *ctx, size_t hashBitLen);

int Skein_256_Update(Skein_256_Ctxt_t *ctx, const uint8_t *msg,
    size_t msgByteCnt);
int Skein_512_Update(Skein_512_Ctxt_t *ctx, const uint8_t *msg,
    size_t msgByteCnt);
int Skein1024_Update(Skein1024_Ctxt_t *ctx, const uint8_t *msg,
    size_t msgByteCnt);

int Skein_256_Final(Skein_256_Ctxt_t *ctx, uint8_t *hashVal);
int Skein_512_Final(Skein_512_Ctxt_t *ctx, uint8_t *hashVal);
int Skein1024_Final(Skein1024_Ctxt_t *ctx, uint8_t *hashVal);

/*
 * Skein APIs for "extended" initialization: MAC keys, tree hashing.
 * After an InitExt() call, just use Update/Final calls as with Init().
 *
 * Notes: Same parameters as _Init() calls, plus treeInfo/key/keyBytes.
 *          When keyBytes == 0 and treeInfo == SKEIN_SEQUENTIAL,
 *              the results of InitExt() are identical to calling Init().
 *          The function Init() may be called once to "precompute" the IV for
 *              a given hashBitLen value, then by saving a copy of the context
 *              the IV computation may be avoided in later calls.
 *          Similarly, the function InitExt() may be called once per MAC key
 *              to precompute the MAC IV, then a copy of the context saved and
 *              reused for each new MAC computation.
 */
int Skein_256_InitExt(Skein_256_Ctxt_t *ctx, size_t hashBitLen,
    uint64_t treeInfo, const uint8_t *key, size_t keyBytes);
int Skein_512_InitExt(Skein_512_Ctxt_t *ctx, size_t hashBitLen,
    uint64_t treeInfo, const uint8_t *key, size_t keyBytes);
int Skein1024_InitExt(Skein1024_Ctxt_t *ctx, size_t hashBitLen,
    uint64_t treeInfo, const uint8_t *key, size_t keyBytes);

/*
 * Skein APIs for MAC and tree hash:
 *      Final_Pad: pad, do final block, but no OUTPUT type
 *      Output:    do just the output stage
 */
int Skein_256_Final_Pad(Skein_256_Ctxt_t *ctx, uint8_t *hashVal);
int Skein_512_Final_Pad(Skein_512_Ctxt_t *ctx, uint8_t *hashVal);
int Skein1024_Final_Pad(Skein1024_Ctxt_t *ctx, uint8_t *hashVal);

#ifndef SKEIN_TREE_HASH
#define SKEIN_TREE_HASH (1)
#endif
#if     SKEIN_TREE_HASH
int Skein_256_Output(Skein_256_Ctxt_t *ctx, uint8_t *hashVal);
int Skein_512_Output(Skein_512_Ctxt_t *ctx, uint8_t *hashVal);
int Skein1024_Output(Skein1024_Ctxt_t *ctx, uint8_t *hashVal);
#endif

/*
 * When you initialize a Skein KCF hashing method you can pass this param
 * structure in cm_param to fine-tune the algorithm's defaults.
 */
typedef struct skein_param {
        size_t  sp_digest_bitlen;               /* length of digest in bits */
} skein_param_t;

/* Module definitions */
#ifdef  SKEIN_MODULE_IMPL
#define CKM_SKEIN_256                           "CKM_SKEIN_256"
#define CKM_SKEIN_512                           "CKM_SKEIN_512"
#define CKM_SKEIN1024                           "CKM_SKEIN1024"
#define CKM_SKEIN_256_MAC                       "CKM_SKEIN_256_MAC"
#define CKM_SKEIN_512_MAC                       "CKM_SKEIN_512_MAC"
#define CKM_SKEIN1024_MAC                       "CKM_SKEIN1024_MAC"

typedef enum skein_mech_type {
        SKEIN_256_MECH_INFO_TYPE,
        SKEIN_512_MECH_INFO_TYPE,
        SKEIN1024_MECH_INFO_TYPE,
        SKEIN_256_MAC_MECH_INFO_TYPE,
        SKEIN_512_MAC_MECH_INFO_TYPE,
        SKEIN1024_MAC_MECH_INFO_TYPE
} skein_mech_type_t;

#define VALID_SKEIN_DIGEST_MECH(__mech)                         \
        ((int)(__mech) >= SKEIN_256_MECH_INFO_TYPE &&           \
        (__mech) <= SKEIN1024_MECH_INFO_TYPE)
#define VALID_SKEIN_MAC_MECH(__mech)                            \
        ((int)(__mech) >= SKEIN_256_MAC_MECH_INFO_TYPE &&       \
        (__mech) <= SKEIN1024_MAC_MECH_INFO_TYPE)
#endif  /* SKEIN_MODULE_IMPL */

#ifdef  __cplusplus
}
#endif

#endif  /* _SYS_SKEIN_H_ */