crypto/modes/ocb128.c - third_party/openssl - Git at Google

 /*
  * Copyright 2014-2016 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
  * in the file LICENSE in the source distribution or at
  * https://www.openssl.org/source/license.html
  */

 #include <string.h>
 #include <openssl/crypto.h>
 #include "modes_lcl.h"

 #ifndef OPENSSL_NO_OCB

 /*
  * Calculate the number of binary trailing zero's in any given number
  */
 static u32 ocb_ntz(u64 n)
 {
     u32 cnt = 0;

     /*
      * We do a right-to-left simple sequential search. This is surprisingly
      * efficient as the distribution of trailing zeros is not uniform,
      * e.g. the number of possible inputs with no trailing zeros is equal to
      * the number with 1 or more; the number with exactly 1 is equal to the
      * number with 2 or more, etc. Checking the last two bits covers 75% of
      * all numbers. Checking the last three covers 87.5%
      */
     while (!(n & 1)) {
         n >>= 1;
         cnt++;
     }
     return cnt;
 }

 /*
  * Shift a block of 16 bytes left by shift bits
  */
 static void ocb_block_lshift(const unsigned char *in, size_t shift,
                              unsigned char *out)
 {
     unsigned char shift_mask;
     int i;
     unsigned char mask[15];

     shift_mask = 0xff;
     shift_mask <<= (8 - shift);
     for (i = 15; i >= 0; i--) {
         if (i > 0) {
             mask[i - 1] = in[i] & shift_mask;
             mask[i - 1] >>= 8 - shift;
         }
         out[i] = in[i] << shift;

         if (i != 15) {
             out[i] ^= mask[i];
         }
     }
 }

 /*
  * Perform a "double" operation as per OCB spec
  */
 static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
 {
     unsigned char mask;

     /*
      * Calculate the mask based on the most significant bit. There are more
      * efficient ways to do this - but this way is constant time
      */
     mask = in->c[0] & 0x80;
     mask >>= 7;
     mask *= 135;

     ocb_block_lshift(in->c, 1, out->c);

     out->c[15] ^= mask;
 }

 /*
  * Perform an xor on in1 and in2 - each of len bytes. Store result in out
  */
 static void ocb_block_xor(const unsigned char *in1,
                           const unsigned char *in2, size_t len,
                           unsigned char *out)
 {
     size_t i;
     for (i = 0; i < len; i++) {
         out[i] = in1[i] ^ in2[i];
     }
 }

 /*
  * Lookup L_index in our lookup table. If we haven't already got it we need to
  * calculate it
  */
 static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT *ctx, size_t idx)
 {
     size_t l_index = ctx->l_index;

     if (idx <= l_index) {
         return ctx->l + idx;
     }

     /* We don't have it - so calculate it */
     if (idx >= ctx->max_l_index) {
         void *tmp_ptr;
         /*
          * Each additional entry allows to process almost double as
          * much data, so that in linear world the table will need to
          * be expanded with smaller and smaller increments. Originally
          * it was doubling in size, which was a waste. Growing it
          * linearly is not formally optimal, but is simpler to implement.
          * We grow table by minimally required 4*n that would accommodate
          * the index.
          */
         ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;
         tmp_ptr =
             OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
         if (tmp_ptr == NULL) /* prevent ctx->l from being clobbered */
             return NULL;
         ctx->l = tmp_ptr;
     }
     while (l_index < idx) {
         ocb_double(ctx->l + l_index, ctx->l + l_index + 1);
         l_index++;
     }
     ctx->l_index = l_index;

     return ctx->l + idx;
 }

 /*
  * Create a new OCB128_CONTEXT
  */
 OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
                                   block128_f encrypt, block128_f decrypt,
                                   ocb128_f stream)
 {
     OCB128_CONTEXT *octx;
     int ret;

     if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {
         ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt,
                                  stream);
         if (ret)
             return octx;
         OPENSSL_free(octx);
     }

     return NULL;
 }

 /*
  * Initialise an existing OCB128_CONTEXT
  */
 int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
                        block128_f encrypt, block128_f decrypt,
                        ocb128_f stream)
 {
     memset(ctx, 0, sizeof(*ctx));
     ctx->l_index = 0;
     ctx->max_l_index = 5;
     ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
     if (ctx->l == NULL)
         return 0;

     /*
      * We set both the encryption and decryption key schedules - decryption
      * needs both. Don't really need decryption schedule if only doing
      * encryption - but it simplifies things to take it anyway
      */
     ctx->encrypt = encrypt;
     ctx->decrypt = decrypt;
     ctx->stream = stream;
     ctx->keyenc = keyenc;
     ctx->keydec = keydec;

     /* L_* = ENCIPHER(K, zeros(128)) */
     ctx->encrypt(ctx->l_star.c, ctx->l_star.c, ctx->keyenc);

     /* L_$ = double(L_*) */
     ocb_double(&ctx->l_star, &ctx->l_dollar);

     /* L_0 = double(L_$) */
     ocb_double(&ctx->l_dollar, ctx->l);

     /* L_{i} = double(L_{i-1}) */
     ocb_double(ctx->l, ctx->l+1);
     ocb_double(ctx->l+1, ctx->l+2);
     ocb_double(ctx->l+2, ctx->l+3);
     ocb_double(ctx->l+3, ctx->l+4);
     ctx->l_index = 4;   /* enough to process up to 496 bytes */

     return 1;
 }

 /*
  * Copy an OCB128_CONTEXT object
  */
 int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
                            void *keyenc, void *keydec)
 {
     memcpy(dest, src, sizeof(OCB128_CONTEXT));
     if (keyenc)
         dest->keyenc = keyenc;
     if (keydec)
         dest->keydec = keydec;
     if (src->l) {
         dest->l = OPENSSL_malloc(src->max_l_index * 16);
         if (dest->l == NULL)
             return 0;
         memcpy(dest->l, src->l, (src->l_index + 1) * 16);
     }
     return 1;
 }

 /*
  * Set the IV to be used for this operation. Must be 1 - 15 bytes.
  */
 int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
                         size_t len, size_t taglen)
 {
     unsigned char ktop[16], tmp[16], mask;
     unsigned char stretch[24], nonce[16];
     size_t bottom, shift;

     /*
      * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
      * We don't support this at this stage
      */
     if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
         return -1;
     }

     /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
     nonce[0] = ((taglen * 8) % 128) << 1;
     memset(nonce + 1, 0, 15);
     memcpy(nonce + 16 - len, iv, len);
     nonce[15 - len] |= 1;

     /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
     memcpy(tmp, nonce, 16);
     tmp[15] &= 0xc0;
     ctx->encrypt(tmp, ktop, ctx->keyenc);

     /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
     memcpy(stretch, ktop, 16);
     ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);

     /* bottom = str2num(Nonce[123..128]) */
     bottom = nonce[15] & 0x3f;

     /* Offset_0 = Stretch[1+bottom..128+bottom] */
     shift = bottom % 8;
     ocb_block_lshift(stretch + (bottom / 8), shift, ctx->offset.c);
     mask = 0xff;
     mask <<= 8 - shift;
     ctx->offset.c[15] |=
         (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);

     return 1;
 }

 /*
  * Provide any AAD. This can be called multiple times. Only the final time can
  * have a partial block
  */
 int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
                       size_t len)
 {
     u64 i, all_num_blocks;
     size_t num_blocks, last_len;
     OCB_BLOCK tmp1;
     OCB_BLOCK tmp2;

     /* Calculate the number of blocks of AAD provided now, and so far */
     num_blocks = len / 16;
     all_num_blocks = num_blocks + ctx->blocks_hashed;

     /* Loop through all full blocks of AAD */
     for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
         OCB_BLOCK *lookup;
         OCB_BLOCK *aad_block;

         /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
         lookup = ocb_lookup_l(ctx, ocb_ntz(i));
         if (lookup == NULL)
             return 0;
         ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);

         /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
         aad_block = (OCB_BLOCK *)(aad + ((i - ctx->blocks_hashed - 1) * 16));
         ocb_block16_xor(&ctx->offset_aad, aad_block, &tmp1);
         ctx->encrypt(tmp1.c, tmp2.c, ctx->keyenc);
         ocb_block16_xor(&ctx->sum, &tmp2, &ctx->sum);
     }

     /*
      * Check if we have any partial blocks left over. This is only valid in the
      * last call to this function
      */
     last_len = len % 16;

     if (last_len > 0) {
         /* Offset_* = Offset_m xor L_* */
         ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);

         /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
         memset(&tmp1, 0, 16);
         memcpy(&tmp1, aad + (num_blocks * 16), last_len);
         ((unsigned char *)&tmp1)[last_len] = 0x80;
         ocb_block16_xor(&ctx->offset_aad, &tmp1, &tmp2);

         /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
         ctx->encrypt(tmp2.c, tmp1.c, ctx->keyenc);
         ocb_block16_xor(&ctx->sum, &tmp1, &ctx->sum);
     }

     ctx->blocks_hashed = all_num_blocks;

     return 1;
 }

 /*
  * Provide any data to be encrypted. This can be called multiple times. Only
  * the final time can have a partial block
  */
 int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
                           const unsigned char *in, unsigned char *out,
                           size_t len)
 {
     u64 i, all_num_blocks;
     size_t num_blocks, last_len;
     OCB_BLOCK tmp1;
     OCB_BLOCK tmp2;
     OCB_BLOCK pad;

     /*
      * Calculate the number of blocks of data to be encrypted provided now, and
      * so far
      */
     num_blocks = len / 16;
     all_num_blocks = num_blocks + ctx->blocks_processed;

     if (num_blocks && all_num_blocks == (size_t)all_num_blocks
         && ctx->stream != NULL) {
         size_t max_idx = 0, top = (size_t)all_num_blocks;

         /*
          * See how many L_{i} entries we need to process data at hand
          * and pre-compute missing entries in the table [if any]...
          */
         while (top >>= 1)
             max_idx++;
         if (ocb_lookup_l(ctx, max_idx) == NULL)
             return 0;

         ctx->stream(in, out, num_blocks, ctx->keyenc,
                     (size_t)ctx->blocks_processed + 1, ctx->offset.c,
                     (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
     } else {
         /* Loop through all full blocks to be encrypted */
         for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
             OCB_BLOCK *lookup;
             OCB_BLOCK *inblock;
             OCB_BLOCK *outblock;

             /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
             lookup = ocb_lookup_l(ctx, ocb_ntz(i));
             if (lookup == NULL)
                 return 0;
             ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);

             /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
             inblock =
                 (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
             ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
             /* Checksum_i = Checksum_{i-1} xor P_i */
             ocb_block16_xor_misaligned(&ctx->checksum, inblock, &ctx->checksum);
             ctx->encrypt(tmp1.c, tmp2.c, ctx->keyenc);
             outblock =
                 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
             ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);
         }
     }

     /*
      * Check if we have any partial blocks left over. This is only valid in the
      * last call to this function
      */
     last_len = len % 16;

     if (last_len > 0) {
         /* Offset_* = Offset_m xor L_* */
         ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);

         /* Pad = ENCIPHER(K, Offset_*) */
         ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);

         /* C_* = P_* xor Pad[1..bitlen(P_*)] */
         ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
                       out + (num_blocks * 16));

         /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
         memset(&tmp1, 0, 16);
         memcpy(&tmp1, in + (len / 16) * 16, last_len);
         ((unsigned char *)(&tmp1))[last_len] = 0x80;
         ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
     }

     ctx->blocks_processed = all_num_blocks;

     return 1;
 }

 /*
  * Provide any data to be decrypted. This can be called multiple times. Only
  * the final time can have a partial block
  */
 int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
                           const unsigned char *in, unsigned char *out,
                           size_t len)
 {
     u64 i, all_num_blocks;
     size_t num_blocks, last_len;
     OCB_BLOCK tmp1;
     OCB_BLOCK tmp2;
     OCB_BLOCK pad;

     /*
      * Calculate the number of blocks of data to be decrypted provided now, and
      * so far
      */
     num_blocks = len / 16;
     all_num_blocks = num_blocks + ctx->blocks_processed;

     if (num_blocks && all_num_blocks == (size_t)all_num_blocks
         && ctx->stream != NULL) {
         size_t max_idx = 0, top = (size_t)all_num_blocks;

         /*
          * See how many L_{i} entries we need to process data at hand
          * and pre-compute missing entries in the table [if any]...
          */
         while (top >>= 1)
             max_idx++;
         if (ocb_lookup_l(ctx, max_idx) == NULL)
             return 0;

         ctx->stream(in, out, num_blocks, ctx->keydec,
                     (size_t)ctx->blocks_processed + 1, ctx->offset.c,
                     (const unsigned char (*)[16])ctx->l, ctx->checksum.c);
     } else {
         /* Loop through all full blocks to be decrypted */
         for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
             OCB_BLOCK *inblock;
             OCB_BLOCK *outblock;

             /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
             OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
             if (lookup == NULL)
                 return 0;
             ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);

             /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
             inblock =
                 (OCB_BLOCK *)(in + ((i - ctx->blocks_processed - 1) * 16));
             ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
             ctx->decrypt(tmp1.c, tmp2.c, ctx->keydec);
             outblock =
                 (OCB_BLOCK *)(out + ((i - ctx->blocks_processed - 1) * 16));
             ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);

             /* Checksum_i = Checksum_{i-1} xor P_i */
             ocb_block16_xor_misaligned(&ctx->checksum, outblock, &ctx->checksum);
         }
     }

     /*
      * Check if we have any partial blocks left over. This is only valid in the
      * last call to this function
      */
     last_len = len % 16;

     if (last_len > 0) {
         /* Offset_* = Offset_m xor L_* */
         ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);

         /* Pad = ENCIPHER(K, Offset_*) */
         ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);

         /* P_* = C_* xor Pad[1..bitlen(C_*)] */
         ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
                       out + (num_blocks * 16));

         /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
         memset(&tmp1, 0, 16);
         memcpy(&tmp1, out + (len / 16) * 16, last_len);
         ((unsigned char *)(&tmp1))[last_len] = 0x80;
         ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
     }

     ctx->blocks_processed = all_num_blocks;

     return 1;
 }

 /*
  * Calculate the tag and verify it against the supplied tag
  */
 int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,
                          size_t len)
 {
     OCB_BLOCK tmp1, tmp2;

     /*
      * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
      */
     ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp1);
     ocb_block16_xor(&tmp1, &ctx->l_dollar, &tmp2);
     ctx->encrypt(tmp2.c, tmp1.c, ctx->keyenc);
     ocb_block16_xor(&tmp1, &ctx->sum, &ctx->tag);

     if (len > 16 || len < 1) {
         return -1;
     }

     /* Compare the tag if we've been given one */
     if (tag)
         return CRYPTO_memcmp(&ctx->tag, tag, len);
     else
         return -1;
 }

 /*
  * Retrieve the calculated tag
  */
 int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)
 {
     if (len > 16 || len < 1) {
         return -1;
     }

     /* Calculate the tag */
     CRYPTO_ocb128_finish(ctx, NULL, 0);

     /* Copy the tag into the supplied buffer */
     memcpy(tag, &ctx->tag, len);

     return 1;
 }

 /*
  * Release all resources
  */
 void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
 {
     if (ctx) {
         OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
         OPENSSL_cleanse(ctx, sizeof(*ctx));
     }
 }

 #endif                          /* OPENSSL_NO_OCB */
	/*
	* Copyright 2014-2016 The OpenSSL Project Authors. All Rights Reserved.
	*
	* Licensed under the OpenSSL license (the "License"). You may not use
	* this file except in compliance with the License. You can obtain a copy
	* in the file LICENSE in the source distribution or at
	* https://www.openssl.org/source/license.html
	*/

	#include <string.h>
	#include <openssl/crypto.h>
	#include "modes_lcl.h"

	#ifndef OPENSSL_NO_OCB

	/*
	* Calculate the number of binary trailing zero's in any given number
	*/
	static u32 ocb_ntz(u64 n)
	{
	u32 cnt = 0;

	/*
	* We do a right-to-left simple sequential search. This is surprisingly
	* efficient as the distribution of trailing zeros is not uniform,
	* e.g. the number of possible inputs with no trailing zeros is equal to
	* the number with 1 or more; the number with exactly 1 is equal to the
	* number with 2 or more, etc. Checking the last two bits covers 75% of
	* all numbers. Checking the last three covers 87.5%
	*/
	while (!(n & 1)) {
	n >>= 1;
	cnt++;
	}
	return cnt;
	}

	/*
	* Shift a block of 16 bytes left by shift bits
	*/
	static void ocb_block_lshift(const unsigned char *in, size_t shift,
	unsigned char *out)
	{
	unsigned char shift_mask;
	int i;
	unsigned char mask[15];

	shift_mask = 0xff;
	shift_mask <<= (8 - shift);
	for (i = 15; i >= 0; i--) {
	if (i > 0) {
	mask[i - 1] = in[i] & shift_mask;
	mask[i - 1] >>= 8 - shift;
	}
	out[i] = in[i] << shift;

	if (i != 15) {
	out[i] ^= mask[i];
	}
	}
	}

	/*
	* Perform a "double" operation as per OCB spec
	*/
	static void ocb_double(OCB_BLOCK in, OCB_BLOCK out)
	{
	unsigned char mask;

	/*
	* Calculate the mask based on the most significant bit. There are more
	* efficient ways to do this - but this way is constant time
	*/
	mask = in->c[0] & 0x80;
	mask >>= 7;
	mask *= 135;

	ocb_block_lshift(in->c, 1, out->c);

	out->c[15] ^= mask;
	}

	/*
	* Perform an xor on in1 and in2 - each of len bytes. Store result in out
	*/
	static void ocb_block_xor(const unsigned char *in1,
	const unsigned char *in2, size_t len,
	unsigned char *out)
	{
	size_t i;
	for (i = 0; i < len; i++) {
	out[i] = in1[i] ^ in2[i];
	}
	}

	/*
	* Lookup L_index in our lookup table. If we haven't already got it we need to
	* calculate it
	*/
	static OCB_BLOCK ocb_lookup_l(OCB128_CONTEXT ctx, size_t idx)
	{
	size_t l_index = ctx->l_index;

	if (idx <= l_index) {
	return ctx->l + idx;
	}

	/* We don't have it - so calculate it */
	if (idx >= ctx->max_l_index) {
	void *tmp_ptr;
	/*
	* Each additional entry allows to process almost double as
	* much data, so that in linear world the table will need to
	* be expanded with smaller and smaller increments. Originally
	* it was doubling in size, which was a waste. Growing it
	* linearly is not formally optimal, but is simpler to implement.
	* We grow table by minimally required 4*n that would accommodate
	* the index.
	*/
	ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;
	tmp_ptr =
	OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
	if (tmp_ptr == NULL) /* prevent ctx->l from being clobbered */
	return NULL;
	ctx->l = tmp_ptr;
	}
	while (l_index < idx) {
	ocb_double(ctx->l + l_index, ctx->l + l_index + 1);
	l_index++;
	}
	ctx->l_index = l_index;

	return ctx->l + idx;
	}

	/*
	* Create a new OCB128_CONTEXT
	*/
	OCB128_CONTEXT CRYPTO_ocb128_new(void keyenc, void *keydec,
	block128_f encrypt, block128_f decrypt,
	ocb128_f stream)
	{
	OCB128_CONTEXT *octx;
	int ret;

	if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {
	ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt,
	stream);
	if (ret)
	return octx;
	OPENSSL_free(octx);
	}

	return NULL;
	}

	/*
	* Initialise an existing OCB128_CONTEXT
	*/
	int CRYPTO_ocb128_init(OCB128_CONTEXT ctx, void keyenc, void *keydec,
	block128_f encrypt, block128_f decrypt,
	ocb128_f stream)
	{
	memset(ctx, 0, sizeof(*ctx));
	ctx->l_index = 0;
	ctx->max_l_index = 5;
	ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
	if (ctx->l == NULL)
	return 0;

	/*
	* We set both the encryption and decryption key schedules - decryption
	* needs both. Don't really need decryption schedule if only doing
	* encryption - but it simplifies things to take it anyway
	*/
	ctx->encrypt = encrypt;
	ctx->decrypt = decrypt;
	ctx->stream = stream;
	ctx->keyenc = keyenc;
	ctx->keydec = keydec;

	/* L_* = ENCIPHER(K, zeros(128)) */
	ctx->encrypt(ctx->l_star.c, ctx->l_star.c, ctx->keyenc);

	/* L_$ = double(L_) /
	ocb_double(&ctx->l_star, &ctx->l_dollar);

	/* L_0 = double(L_$) */
	ocb_double(&ctx->l_dollar, ctx->l);

	/* L_{i} = double(L_{i-1}) */
	ocb_double(ctx->l, ctx->l+1);
	ocb_double(ctx->l+1, ctx->l+2);
	ocb_double(ctx->l+2, ctx->l+3);
	ocb_double(ctx->l+3, ctx->l+4);
	ctx->l_index = 4; /* enough to process up to 496 bytes */

	return 1;
	}

	/*
	* Copy an OCB128_CONTEXT object
	*/
	int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT dest, OCB128_CONTEXT src,
	void keyenc, void keydec)
	{
	memcpy(dest, src, sizeof(OCB128_CONTEXT));
	if (keyenc)
	dest->keyenc = keyenc;
	if (keydec)
	dest->keydec = keydec;
	if (src->l) {
	dest->l = OPENSSL_malloc(src->max_l_index * 16);
	if (dest->l == NULL)
	return 0;
	memcpy(dest->l, src->l, (src->l_index + 1) * 16);
	}
	return 1;
	}

	/*
	* Set the IV to be used for this operation. Must be 1 - 15 bytes.
	*/
	int CRYPTO_ocb128_setiv(OCB128_CONTEXT ctx, const unsigned char iv,
	size_t len, size_t taglen)
	{
	unsigned char ktop[16], tmp[16], mask;
	unsigned char stretch[24], nonce[16];
	size_t bottom, shift;

	/*
	* Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
	* We don't support this at this stage
	*/
	if ((len > 15) \|\| (len < 1) \|\| (taglen > 16) \|\| (taglen < 1)) {
	return -1;
	}

	/* Nonce = num2str(TAGLEN mod 128,7) \|\| zeros(120-bitlen(N)) \|\| 1 \|\| N */
	nonce[0] = ((taglen * 8) % 128) << 1;
	memset(nonce + 1, 0, 15);
	memcpy(nonce + 16 - len, iv, len);
	nonce[15 - len] \|= 1;

	/* Ktop = ENCIPHER(K, Nonce[1..122] \|\| zeros(6)) */
	memcpy(tmp, nonce, 16);
	tmp[15] &= 0xc0;
	ctx->encrypt(tmp, ktop, ctx->keyenc);

	/* Stretch = Ktop \|\| (Ktop[1..64] xor Ktop[9..72]) */
	memcpy(stretch, ktop, 16);
	ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);

	/* bottom = str2num(Nonce[123..128]) */
	bottom = nonce[15] & 0x3f;

	/* Offset_0 = Stretch[1+bottom..128+bottom] */
	shift = bottom % 8;
	ocb_block_lshift(stretch + (bottom / 8), shift, ctx->offset.c);
	mask = 0xff;
	mask <<= 8 - shift;
	ctx->offset.c[15] \|=
	(*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);

	return 1;
	}

	/*
	* Provide any AAD. This can be called multiple times. Only the final time can
	* have a partial block
	*/
	int CRYPTO_ocb128_aad(OCB128_CONTEXT ctx, const unsigned char aad,
	size_t len)
	{
	u64 i, all_num_blocks;
	size_t num_blocks, last_len;
	OCB_BLOCK tmp1;
	OCB_BLOCK tmp2;

	/* Calculate the number of blocks of AAD provided now, and so far */
	num_blocks = len / 16;
	all_num_blocks = num_blocks + ctx->blocks_hashed;

	/* Loop through all full blocks of AAD */
	for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
	OCB_BLOCK *lookup;
	OCB_BLOCK *aad_block;

	/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
	lookup = ocb_lookup_l(ctx, ocb_ntz(i));
	if (lookup == NULL)
	return 0;
	ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);

	/* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
	aad_block = (OCB_BLOCK )(aad + ((i - ctx->blocks_hashed - 1) 16));
	ocb_block16_xor(&ctx->offset_aad, aad_block, &tmp1);
	ctx->encrypt(tmp1.c, tmp2.c, ctx->keyenc);
	ocb_block16_xor(&ctx->sum, &tmp2, &ctx->sum);
	}

	/*
	* Check if we have any partial blocks left over. This is only valid in the
	* last call to this function
	*/
	last_len = len % 16;

	if (last_len > 0) {
	/* Offset_* = Offset_m xor L_* */
	ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);

	/* CipherInput = (A_* \|\| 1 \|\| zeros(127-bitlen(A_))) xor Offset_ */
	memset(&tmp1, 0, 16);
	memcpy(&tmp1, aad + (num_blocks * 16), last_len);
	((unsigned char *)&tmp1)[last_len] = 0x80;
	ocb_block16_xor(&ctx->offset_aad, &tmp1, &tmp2);

	/* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
	ctx->encrypt(tmp2.c, tmp1.c, ctx->keyenc);
	ocb_block16_xor(&ctx->sum, &tmp1, &ctx->sum);
	}

	ctx->blocks_hashed = all_num_blocks;

	return 1;
	}

	/*
	* Provide any data to be encrypted. This can be called multiple times. Only
	* the final time can have a partial block
	*/
	int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
	const unsigned char in, unsigned char out,
	size_t len)
	{
	u64 i, all_num_blocks;
	size_t num_blocks, last_len;
	OCB_BLOCK tmp1;
	OCB_BLOCK tmp2;
	OCB_BLOCK pad;

	/*
	* Calculate the number of blocks of data to be encrypted provided now, and
	* so far
	*/
	num_blocks = len / 16;
	all_num_blocks = num_blocks + ctx->blocks_processed;

	if (num_blocks && all_num_blocks == (size_t)all_num_blocks
	&& ctx->stream != NULL) {
	size_t max_idx = 0, top = (size_t)all_num_blocks;

	/*
	* See how many L_{i} entries we need to process data at hand
	* and pre-compute missing entries in the table [if any]...
	*/
	while (top >>= 1)
	max_idx++;
	if (ocb_lookup_l(ctx, max_idx) == NULL)
	return 0;

	ctx->stream(in, out, num_blocks, ctx->keyenc,
	(size_t)ctx->blocks_processed + 1, ctx->offset.c,
	(const unsigned char (*)[16])ctx->l, ctx->checksum.c);
	} else {
	/* Loop through all full blocks to be encrypted */
	for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
	OCB_BLOCK *lookup;
	OCB_BLOCK *inblock;
	OCB_BLOCK *outblock;

	/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
	lookup = ocb_lookup_l(ctx, ocb_ntz(i));
	if (lookup == NULL)
	return 0;
	ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);

	/* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
	inblock =
	(OCB_BLOCK )(in + ((i - ctx->blocks_processed - 1) 16));
	ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
	/* Checksum_i = Checksum_{i-1} xor P_i */
	ocb_block16_xor_misaligned(&ctx->checksum, inblock, &ctx->checksum);
	ctx->encrypt(tmp1.c, tmp2.c, ctx->keyenc);
	outblock =
	(OCB_BLOCK )(out + ((i - ctx->blocks_processed - 1) 16));
	ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);
	}
	}

	/*
	* Check if we have any partial blocks left over. This is only valid in the
	* last call to this function
	*/
	last_len = len % 16;

	if (last_len > 0) {
	/* Offset_* = Offset_m xor L_* */
	ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);

	/* Pad = ENCIPHER(K, Offset_) /
	ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);

	/* C_* = P_* xor Pad[1..bitlen(P_)] /
	ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
	out + (num_blocks * 16));

	/* Checksum_* = Checksum_m xor (P_* \|\| 1 \|\| zeros(127-bitlen(P_))) /
	memset(&tmp1, 0, 16);
	memcpy(&tmp1, in + (len / 16) * 16, last_len);
	((unsigned char *)(&tmp1))[last_len] = 0x80;
	ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
	}

	ctx->blocks_processed = all_num_blocks;

	return 1;
	}

	/*
	* Provide any data to be decrypted. This can be called multiple times. Only
	* the final time can have a partial block
	*/
	int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
	const unsigned char in, unsigned char out,
	size_t len)
	{
	u64 i, all_num_blocks;
	size_t num_blocks, last_len;
	OCB_BLOCK tmp1;
	OCB_BLOCK tmp2;
	OCB_BLOCK pad;

	/*
	* Calculate the number of blocks of data to be decrypted provided now, and
	* so far
	*/
	num_blocks = len / 16;
	all_num_blocks = num_blocks + ctx->blocks_processed;

	if (num_blocks && all_num_blocks == (size_t)all_num_blocks
	&& ctx->stream != NULL) {
	size_t max_idx = 0, top = (size_t)all_num_blocks;

	/*
	* See how many L_{i} entries we need to process data at hand
	* and pre-compute missing entries in the table [if any]...
	*/
	while (top >>= 1)
	max_idx++;
	if (ocb_lookup_l(ctx, max_idx) == NULL)
	return 0;

	ctx->stream(in, out, num_blocks, ctx->keydec,
	(size_t)ctx->blocks_processed + 1, ctx->offset.c,
	(const unsigned char (*)[16])ctx->l, ctx->checksum.c);
	} else {
	/* Loop through all full blocks to be decrypted */
	for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
	OCB_BLOCK *inblock;
	OCB_BLOCK *outblock;

	/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
	OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
	if (lookup == NULL)
	return 0;
	ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);

	/* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
	inblock =
	(OCB_BLOCK )(in + ((i - ctx->blocks_processed - 1) 16));
	ocb_block16_xor_misaligned(&ctx->offset, inblock, &tmp1);
	ctx->decrypt(tmp1.c, tmp2.c, ctx->keydec);
	outblock =
	(OCB_BLOCK )(out + ((i - ctx->blocks_processed - 1) 16));
	ocb_block16_xor_misaligned(&ctx->offset, &tmp2, outblock);

	/* Checksum_i = Checksum_{i-1} xor P_i */
	ocb_block16_xor_misaligned(&ctx->checksum, outblock, &ctx->checksum);
	}
	}

	/*
	* Check if we have any partial blocks left over. This is only valid in the
	* last call to this function
	*/
	last_len = len % 16;

	if (last_len > 0) {
	/* Offset_* = Offset_m xor L_* */
	ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);

	/* Pad = ENCIPHER(K, Offset_) /
	ctx->encrypt(ctx->offset.c, pad.c, ctx->keyenc);

	/* P_* = C_* xor Pad[1..bitlen(C_)] /
	ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
	out + (num_blocks * 16));

	/* Checksum_* = Checksum_m xor (P_* \|\| 1 \|\| zeros(127-bitlen(P_))) /
	memset(&tmp1, 0, 16);
	memcpy(&tmp1, out + (len / 16) * 16, last_len);
	((unsigned char *)(&tmp1))[last_len] = 0x80;
	ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
	}

	ctx->blocks_processed = all_num_blocks;

	return 1;
	}

	/*
	* Calculate the tag and verify it against the supplied tag
	*/
	int CRYPTO_ocb128_finish(OCB128_CONTEXT ctx, const unsigned char tag,
	size_t len)
	{
	OCB_BLOCK tmp1, tmp2;

	/*
	* Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
	*/
	ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp1);
	ocb_block16_xor(&tmp1, &ctx->l_dollar, &tmp2);
	ctx->encrypt(tmp2.c, tmp1.c, ctx->keyenc);
	ocb_block16_xor(&tmp1, &ctx->sum, &ctx->tag);

	if (len > 16 \|\| len < 1) {
	return -1;
	}

	/* Compare the tag if we've been given one */
	if (tag)
	return CRYPTO_memcmp(&ctx->tag, tag, len);
	else
	return -1;
	}

	/*
	* Retrieve the calculated tag
	*/
	int CRYPTO_ocb128_tag(OCB128_CONTEXT ctx, unsigned char tag, size_t len)
	{
	if (len > 16 \|\| len < 1) {
	return -1;
	}

	/* Calculate the tag */
	CRYPTO_ocb128_finish(ctx, NULL, 0);

	/* Copy the tag into the supplied buffer */
	memcpy(tag, &ctx->tag, len);

	return 1;
	}

	/*
	* Release all resources
	*/
	void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)
	{
	if (ctx) {
	OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);
	OPENSSL_cleanse(ctx, sizeof(*ctx));
	}
	}

	#endif /* OPENSSL_NO_OCB */