library/poly1305.c - mirror/mbed-tls.git - TrustedFirmware Git Browser

 /**
  * \file poly1305.c
  *
  * \brief Poly1305 authentication algorithm.
  *
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */
 #include "common.h"

 #if defined(MBEDTLS_POLY1305_C)

 #include "mbedtls/poly1305.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"

 #include <string.h>

 #if defined(MBEDTLS_SELF_TEST)
 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
 #define mbedtls_printf printf
 #endif /* MBEDTLS_PLATFORM_C */
 #endif /* MBEDTLS_SELF_TEST */

 #if !defined(MBEDTLS_POLY1305_ALT)

 #if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
     !defined(inline) && !defined(__cplusplus)
 #define inline __inline
 #endif

 /* Parameter validation macros */
 #define POLY1305_VALIDATE_RET( cond )                                       \
     MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA )
 #define POLY1305_VALIDATE( cond )                                           \
     MBEDTLS_INTERNAL_VALIDATE( cond )

 #define POLY1305_BLOCK_SIZE_BYTES ( 16U )

 /*
  * Our implementation is tuned for 32-bit platforms with a 64-bit multiplier.
  * However we provided an alternative for platforms without such a multiplier.
  */
 #if defined(MBEDTLS_NO_64BIT_MULTIPLICATION)
 static uint64_t mul64( uint32_t a, uint32_t b )
 {
     /* a = al + 2**16 ah, b = bl + 2**16 bh */
     const uint16_t al = (uint16_t) a;
     const uint16_t bl = (uint16_t) b;
     const uint16_t ah = a >> 16;
     const uint16_t bh = b >> 16;

     /* ab = al*bl + 2**16 (ah*bl + bl*bh) + 2**32 ah*bh */
     const uint32_t lo = (uint32_t) al * bl;
     const uint64_t me = (uint64_t)( (uint32_t) ah * bl ) + (uint32_t) al * bh;
     const uint32_t hi = (uint32_t) ah * bh;

     return( lo + ( me << 16 ) + ( (uint64_t) hi << 32 ) );
 }
 #else
 static inline uint64_t mul64( uint32_t a, uint32_t b )
 {
     return( (uint64_t) a * b );
 }
 #endif


 /**
  * \brief                   Process blocks with Poly1305.
  *
  * \param ctx               The Poly1305 context.
  * \param nblocks           Number of blocks to process. Note that this
  *                          function only processes full blocks.
  * \param input             Buffer containing the input block(s).
  * \param needs_padding     Set to 0 if the padding bit has already been
  *                          applied to the input data before calling this
  *                          function.  Otherwise, set this parameter to 1.
  */
 static void poly1305_process( mbedtls_poly1305_context *ctx,
                               size_t nblocks,
                               const unsigned char *input,
                               uint32_t needs_padding )
 {
     uint64_t d0, d1, d2, d3;
     uint32_t acc0, acc1, acc2, acc3, acc4;
     uint32_t r0, r1, r2, r3;
     uint32_t rs1, rs2, rs3;
     size_t offset  = 0U;
     size_t i;

     r0 = ctx->r[0];
     r1 = ctx->r[1];
     r2 = ctx->r[2];
     r3 = ctx->r[3];

     rs1 = r1 + ( r1 >> 2U );
     rs2 = r2 + ( r2 >> 2U );
     rs3 = r3 + ( r3 >> 2U );

     acc0 = ctx->acc[0];
     acc1 = ctx->acc[1];
     acc2 = ctx->acc[2];
     acc3 = ctx->acc[3];
     acc4 = ctx->acc[4];

     /* Process full blocks */
     for( i = 0U; i < nblocks; i++ )
     {
         /* The input block is treated as a 128-bit little-endian integer */
         d0   = MBEDTLS_GET_UINT32_LE( input, offset + 0  );
         d1   = MBEDTLS_GET_UINT32_LE( input, offset + 4  );
         d2   = MBEDTLS_GET_UINT32_LE( input, offset + 8  );
         d3   = MBEDTLS_GET_UINT32_LE( input, offset + 12 );

         /* Compute: acc += (padded) block as a 130-bit integer */
         d0  += (uint64_t) acc0;
         d1  += (uint64_t) acc1 + ( d0 >> 32U );
         d2  += (uint64_t) acc2 + ( d1 >> 32U );
         d3  += (uint64_t) acc3 + ( d2 >> 32U );
         acc0 = (uint32_t) d0;
         acc1 = (uint32_t) d1;
         acc2 = (uint32_t) d2;
         acc3 = (uint32_t) d3;
         acc4 += (uint32_t) ( d3 >> 32U ) + needs_padding;

         /* Compute: acc *= r */
         d0 = mul64( acc0, r0  ) +
              mul64( acc1, rs3 ) +
              mul64( acc2, rs2 ) +
              mul64( acc3, rs1 );
         d1 = mul64( acc0, r1  ) +
              mul64( acc1, r0  ) +
              mul64( acc2, rs3 ) +
              mul64( acc3, rs2 ) +
              mul64( acc4, rs1 );
         d2 = mul64( acc0, r2  ) +
              mul64( acc1, r1  ) +
              mul64( acc2, r0  ) +
              mul64( acc3, rs3 ) +
              mul64( acc4, rs2 );
         d3 = mul64( acc0, r3  ) +
              mul64( acc1, r2  ) +
              mul64( acc2, r1  ) +
              mul64( acc3, r0  ) +
              mul64( acc4, rs3 );
         acc4 *= r0;

         /* Compute: acc %= (2^130 - 5) (partial remainder) */
         d1 += ( d0 >> 32 );
         d2 += ( d1 >> 32 );
         d3 += ( d2 >> 32 );
         acc0 = (uint32_t) d0;
         acc1 = (uint32_t) d1;
         acc2 = (uint32_t) d2;
         acc3 = (uint32_t) d3;
         acc4 = (uint32_t) ( d3 >> 32 ) + acc4;

         d0 = (uint64_t) acc0 + ( acc4 >> 2 ) + ( acc4 & 0xFFFFFFFCU );
         acc4 &= 3U;
         acc0 = (uint32_t) d0;
         d0 = (uint64_t) acc1 + ( d0 >> 32U );
         acc1 = (uint32_t) d0;
         d0 = (uint64_t) acc2 + ( d0 >> 32U );
         acc2 = (uint32_t) d0;
         d0 = (uint64_t) acc3 + ( d0 >> 32U );
         acc3 = (uint32_t) d0;
         d0 = (uint64_t) acc4 + ( d0 >> 32U );
         acc4 = (uint32_t) d0;

         offset    += POLY1305_BLOCK_SIZE_BYTES;
     }

     ctx->acc[0] = acc0;
     ctx->acc[1] = acc1;
     ctx->acc[2] = acc2;
     ctx->acc[3] = acc3;
     ctx->acc[4] = acc4;
 }

 /**
  * \brief                   Compute the Poly1305 MAC
  *
  * \param ctx               The Poly1305 context.
  * \param mac               The buffer to where the MAC is written. Must be
  *                          big enough to contain the 16-byte MAC.
  */
 static void poly1305_compute_mac( const mbedtls_poly1305_context *ctx,
                                   unsigned char mac[16] )
 {
     uint64_t d;
     uint32_t g0, g1, g2, g3, g4;
     uint32_t acc0, acc1, acc2, acc3, acc4;
     uint32_t mask;
     uint32_t mask_inv;

     acc0 = ctx->acc[0];
     acc1 = ctx->acc[1];
     acc2 = ctx->acc[2];
     acc3 = ctx->acc[3];
     acc4 = ctx->acc[4];

     /* Before adding 's' we ensure that the accumulator is mod 2^130 - 5.
      * We do this by calculating acc - (2^130 - 5), then checking if
      * the 131st bit is set. If it is, then reduce: acc -= (2^130 - 5)
      */

     /* Calculate acc + -(2^130 - 5) */
     d  = ( (uint64_t) acc0 + 5U );
     g0 = (uint32_t) d;
     d  = ( (uint64_t) acc1 + ( d >> 32 ) );
     g1 = (uint32_t) d;
     d  = ( (uint64_t) acc2 + ( d >> 32 ) );
     g2 = (uint32_t) d;
     d  = ( (uint64_t) acc3 + ( d >> 32 ) );
     g3 = (uint32_t) d;
     g4 = acc4 + (uint32_t) ( d >> 32U );

     /* mask == 0xFFFFFFFF if 131st bit is set, otherwise mask == 0 */
     mask = (uint32_t) 0U - ( g4 >> 2U );
     mask_inv = ~mask;

     /* If 131st bit is set then acc=g, otherwise, acc is unmodified */
     acc0 = ( acc0 & mask_inv ) | ( g0 & mask );
     acc1 = ( acc1 & mask_inv ) | ( g1 & mask );
     acc2 = ( acc2 & mask_inv ) | ( g2 & mask );
     acc3 = ( acc3 & mask_inv ) | ( g3 & mask );

     /* Add 's' */
     d = (uint64_t) acc0 + ctx->s[0];
     acc0 = (uint32_t) d;
     d = (uint64_t) acc1 + ctx->s[1] + ( d >> 32U );
     acc1 = (uint32_t) d;
     d = (uint64_t) acc2 + ctx->s[2] + ( d >> 32U );
     acc2 = (uint32_t) d;
     acc3 += ctx->s[3] + (uint32_t) ( d >> 32U );

     /* Compute MAC (128 least significant bits of the accumulator) */
     MBEDTLS_PUT_UINT32_LE( acc0, mac,  0 );
     MBEDTLS_PUT_UINT32_LE( acc1, mac,  4 );
     MBEDTLS_PUT_UINT32_LE( acc2, mac,  8 );
     MBEDTLS_PUT_UINT32_LE( acc3, mac, 12 );
 }

 void mbedtls_poly1305_init( mbedtls_poly1305_context *ctx )
 {
     POLY1305_VALIDATE( ctx != NULL );

     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
 }

 void mbedtls_poly1305_free( mbedtls_poly1305_context *ctx )
 {
     if( ctx == NULL )
         return;

     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
 }

 int mbedtls_poly1305_starts( mbedtls_poly1305_context *ctx,
                              const unsigned char key[32] )
 {
     POLY1305_VALIDATE_RET( ctx != NULL );
     POLY1305_VALIDATE_RET( key != NULL );

     /* r &= 0x0ffffffc0ffffffc0ffffffc0fffffff */
     ctx->r[0] = MBEDTLS_GET_UINT32_LE( key, 0 )  & 0x0FFFFFFFU;
     ctx->r[1] = MBEDTLS_GET_UINT32_LE( key, 4 )  & 0x0FFFFFFCU;
     ctx->r[2] = MBEDTLS_GET_UINT32_LE( key, 8 )  & 0x0FFFFFFCU;
     ctx->r[3] = MBEDTLS_GET_UINT32_LE( key, 12 ) & 0x0FFFFFFCU;

     ctx->s[0] = MBEDTLS_GET_UINT32_LE( key, 16 );
     ctx->s[1] = MBEDTLS_GET_UINT32_LE( key, 20 );
     ctx->s[2] = MBEDTLS_GET_UINT32_LE( key, 24 );
     ctx->s[3] = MBEDTLS_GET_UINT32_LE( key, 28 );

     /* Initial accumulator state */
     ctx->acc[0] = 0U;
     ctx->acc[1] = 0U;
     ctx->acc[2] = 0U;
     ctx->acc[3] = 0U;
     ctx->acc[4] = 0U;

     /* Queue initially empty */
     mbedtls_platform_zeroize( ctx->queue, sizeof( ctx->queue ) );
     ctx->queue_len = 0U;

     return( 0 );
 }

 int mbedtls_poly1305_update( mbedtls_poly1305_context *ctx,
                              const unsigned char *input,
                              size_t ilen )
 {
     size_t offset    = 0U;
     size_t remaining = ilen;
     size_t queue_free_len;
     size_t nblocks;
     POLY1305_VALIDATE_RET( ctx != NULL );
     POLY1305_VALIDATE_RET( ilen == 0 || input != NULL );

     if( ( remaining > 0U ) && ( ctx->queue_len > 0U ) )
     {
         queue_free_len = ( POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );

         if( ilen < queue_free_len )
         {
             /* Not enough data to complete the block.
              * Store this data with the other leftovers.
              */
             memcpy( &ctx->queue[ctx->queue_len],
                     input,
                     ilen );

             ctx->queue_len += ilen;

             remaining = 0U;
         }
         else
         {
             /* Enough data to produce a complete block */
             memcpy( &ctx->queue[ctx->queue_len],
                     input,
                     queue_free_len );

             ctx->queue_len = 0U;

             poly1305_process( ctx, 1U, ctx->queue, 1U ); /* add padding bit */

             offset    += queue_free_len;
             remaining -= queue_free_len;
         }
     }

     if( remaining >= POLY1305_BLOCK_SIZE_BYTES )
     {
         nblocks = remaining / POLY1305_BLOCK_SIZE_BYTES;

         poly1305_process( ctx, nblocks, &input[offset], 1U );

         offset += nblocks * POLY1305_BLOCK_SIZE_BYTES;
         remaining %= POLY1305_BLOCK_SIZE_BYTES;
     }

     if( remaining > 0U )
     {
         /* Store partial block */
         ctx->queue_len = remaining;
         memcpy( ctx->queue, &input[offset], remaining );
     }

     return( 0 );
 }

 int mbedtls_poly1305_finish( mbedtls_poly1305_context *ctx,
                              unsigned char mac[16] )
 {
     POLY1305_VALIDATE_RET( ctx != NULL );
     POLY1305_VALIDATE_RET( mac != NULL );

     /* Process any leftover data */
     if( ctx->queue_len > 0U )
     {
         /* Add padding bit */
         ctx->queue[ctx->queue_len] = 1U;
         ctx->queue_len++;

         /* Pad with zeroes */
         memset( &ctx->queue[ctx->queue_len],
                 0,
                 POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );

         poly1305_process( ctx, 1U,          /* Process 1 block */
                           ctx->queue, 0U ); /* Already padded above */
     }

     poly1305_compute_mac( ctx, mac );

     return( 0 );
 }

 int mbedtls_poly1305_mac( const unsigned char key[32],
                           const unsigned char *input,
                           size_t ilen,
                           unsigned char mac[16] )
 {
     mbedtls_poly1305_context ctx;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     POLY1305_VALIDATE_RET( key != NULL );
     POLY1305_VALIDATE_RET( mac != NULL );
     POLY1305_VALIDATE_RET( ilen == 0 || input != NULL );

     mbedtls_poly1305_init( &ctx );

     ret = mbedtls_poly1305_starts( &ctx, key );
     if( ret != 0 )
         goto cleanup;

     ret = mbedtls_poly1305_update( &ctx, input, ilen );
     if( ret != 0 )
         goto cleanup;

     ret = mbedtls_poly1305_finish( &ctx, mac );

 cleanup:
     mbedtls_poly1305_free( &ctx );
     return( ret );
 }

 #endif /* MBEDTLS_POLY1305_ALT */

 #if defined(MBEDTLS_SELF_TEST)

 static const unsigned char test_keys[2][32] =
 {
     {
         0x85, 0xd6, 0xbe, 0x78, 0x57, 0x55, 0x6d, 0x33,
         0x7f, 0x44, 0x52, 0xfe, 0x42, 0xd5, 0x06, 0xa8,
         0x01, 0x03, 0x80, 0x8a, 0xfb, 0x0d, 0xb2, 0xfd,
         0x4a, 0xbf, 0xf6, 0xaf, 0x41, 0x49, 0xf5, 0x1b
     },
     {
         0x1c, 0x92, 0x40, 0xa5, 0xeb, 0x55, 0xd3, 0x8a,
         0xf3, 0x33, 0x88, 0x86, 0x04, 0xf6, 0xb5, 0xf0,
         0x47, 0x39, 0x17, 0xc1, 0x40, 0x2b, 0x80, 0x09,
         0x9d, 0xca, 0x5c, 0xbc, 0x20, 0x70, 0x75, 0xc0
     }
 };

 static const unsigned char test_data[2][127] =
 {
     {
         0x43, 0x72, 0x79, 0x70, 0x74, 0x6f, 0x67, 0x72,
         0x61, 0x70, 0x68, 0x69, 0x63, 0x20, 0x46, 0x6f,
         0x72, 0x75, 0x6d, 0x20, 0x52, 0x65, 0x73, 0x65,
         0x61, 0x72, 0x63, 0x68, 0x20, 0x47, 0x72, 0x6f,
         0x75, 0x70
     },
     {
         0x27, 0x54, 0x77, 0x61, 0x73, 0x20, 0x62, 0x72,
         0x69, 0x6c, 0x6c, 0x69, 0x67, 0x2c, 0x20, 0x61,
         0x6e, 0x64, 0x20, 0x74, 0x68, 0x65, 0x20, 0x73,
         0x6c, 0x69, 0x74, 0x68, 0x79, 0x20, 0x74, 0x6f,
         0x76, 0x65, 0x73, 0x0a, 0x44, 0x69, 0x64, 0x20,
         0x67, 0x79, 0x72, 0x65, 0x20, 0x61, 0x6e, 0x64,
         0x20, 0x67, 0x69, 0x6d, 0x62, 0x6c, 0x65, 0x20,
         0x69, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x77,
         0x61, 0x62, 0x65, 0x3a, 0x0a, 0x41, 0x6c, 0x6c,
         0x20, 0x6d, 0x69, 0x6d, 0x73, 0x79, 0x20, 0x77,
         0x65, 0x72, 0x65, 0x20, 0x74, 0x68, 0x65, 0x20,
         0x62, 0x6f, 0x72, 0x6f, 0x67, 0x6f, 0x76, 0x65,
         0x73, 0x2c, 0x0a, 0x41, 0x6e, 0x64, 0x20, 0x74,
         0x68, 0x65, 0x20, 0x6d, 0x6f, 0x6d, 0x65, 0x20,
         0x72, 0x61, 0x74, 0x68, 0x73, 0x20, 0x6f, 0x75,
         0x74, 0x67, 0x72, 0x61, 0x62, 0x65, 0x2e
     }
 };

 static const size_t test_data_len[2] =
 {
     34U,
     127U
 };

 static const unsigned char test_mac[2][16] =
 {
     {
         0xa8, 0x06, 0x1d, 0xc1, 0x30, 0x51, 0x36, 0xc6,
         0xc2, 0x2b, 0x8b, 0xaf, 0x0c, 0x01, 0x27, 0xa9
     },
     {
         0x45, 0x41, 0x66, 0x9a, 0x7e, 0xaa, 0xee, 0x61,
         0xe7, 0x08, 0xdc, 0x7c, 0xbc, 0xc5, 0xeb, 0x62
     }
 };

 /* Make sure no other definition is already present. */
 #undef ASSERT

 #define ASSERT( cond, args )            \
     do                                  \
     {                                   \
         if( ! ( cond ) )                \
         {                               \
             if( verbose != 0 )          \
                 mbedtls_printf args;    \
                                         \
             return( -1 );               \
         }                               \
     }                                   \
     while( 0 )

 int mbedtls_poly1305_self_test( int verbose )
 {
     unsigned char mac[16];
     unsigned i;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     for( i = 0U; i < 2U; i++ )
     {
         if( verbose != 0 )
             mbedtls_printf( "  Poly1305 test %u ", i );

         ret = mbedtls_poly1305_mac( test_keys[i],
                                     test_data[i],
                                     test_data_len[i],
                                     mac );
         ASSERT( 0 == ret, ( "error code: %i\n", ret ) );

         ASSERT( 0 == memcmp( mac, test_mac[i], 16U ), ( "failed (mac)\n" ) );

         if( verbose != 0 )
             mbedtls_printf( "passed\n" );
     }

     if( verbose != 0 )
         mbedtls_printf( "\n" );

     return( 0 );
 }

 #endif /* MBEDTLS_SELF_TEST */

 #endif /* MBEDTLS_POLY1305_C */
	/**
	* \file poly1305.c
	*
	* \brief Poly1305 authentication algorithm.
	*
	* Copyright The Mbed TLS Contributors
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	#include "common.h"

	#if defined(MBEDTLS_POLY1305_C)

	#include "mbedtls/poly1305.h"
	#include "mbedtls/platform_util.h"
	#include "mbedtls/error.h"

	#include <string.h>

	#if defined(MBEDTLS_SELF_TEST)
	#if defined(MBEDTLS_PLATFORM_C)
	#include "mbedtls/platform.h"
	#else
	#include <stdio.h>
	#define mbedtls_printf printf
	#endif /* MBEDTLS_PLATFORM_C */
	#endif /* MBEDTLS_SELF_TEST */

	#if !defined(MBEDTLS_POLY1305_ALT)

	#if ( defined(__ARMCC_VERSION) \|\| defined(_MSC_VER) ) && \
	!defined(inline) && !defined(__cplusplus)
	#define inline __inline
	#endif

	/* Parameter validation macros */
	#define POLY1305_VALIDATE_RET( cond ) \
	MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA )
	#define POLY1305_VALIDATE( cond ) \
	MBEDTLS_INTERNAL_VALIDATE( cond )

	#define POLY1305_BLOCK_SIZE_BYTES ( 16U )

	/*
	* Our implementation is tuned for 32-bit platforms with a 64-bit multiplier.
	* However we provided an alternative for platforms without such a multiplier.
	*/
	#if defined(MBEDTLS_NO_64BIT_MULTIPLICATION)
	static uint64_t mul64( uint32_t a, uint32_t b )
	{
	/* a = al + 216 ah, b = bl + 216 bh */
	const uint16_t al = (uint16_t) a;
	const uint16_t bl = (uint16_t) b;
	const uint16_t ah = a >> 16;
	const uint16_t bh = b >> 16;

	/* ab = albl + 216 (ahbl + blbh) + 232 ahbh */
	const uint32_t lo = (uint32_t) al * bl;
	const uint64_t me = (uint64_t)( (uint32_t) ah * bl ) + (uint32_t) al * bh;
	const uint32_t hi = (uint32_t) ah * bh;

	return( lo + ( me << 16 ) + ( (uint64_t) hi << 32 ) );
	}
	#else
	static inline uint64_t mul64( uint32_t a, uint32_t b )
	{
	return( (uint64_t) a * b );
	}
	#endif


	/**
	* \brief Process blocks with Poly1305.
	*
	* \param ctx The Poly1305 context.
	* \param nblocks Number of blocks to process. Note that this
	* function only processes full blocks.
	* \param input Buffer containing the input block(s).
	* \param needs_padding Set to 0 if the padding bit has already been
	* applied to the input data before calling this
	* function. Otherwise, set this parameter to 1.
	*/
	static void poly1305_process( mbedtls_poly1305_context *ctx,
	size_t nblocks,
	const unsigned char *input,
	uint32_t needs_padding )
	{
	uint64_t d0, d1, d2, d3;
	uint32_t acc0, acc1, acc2, acc3, acc4;
	uint32_t r0, r1, r2, r3;
	uint32_t rs1, rs2, rs3;
	size_t offset = 0U;
	size_t i;

	r0 = ctx->r[0];
	r1 = ctx->r[1];
	r2 = ctx->r[2];
	r3 = ctx->r[3];

	rs1 = r1 + ( r1 >> 2U );
	rs2 = r2 + ( r2 >> 2U );
	rs3 = r3 + ( r3 >> 2U );

	acc0 = ctx->acc[0];
	acc1 = ctx->acc[1];
	acc2 = ctx->acc[2];
	acc3 = ctx->acc[3];
	acc4 = ctx->acc[4];

	/* Process full blocks */
	for( i = 0U; i < nblocks; i++ )
	{
	/* The input block is treated as a 128-bit little-endian integer */
	d0 = MBEDTLS_GET_UINT32_LE( input, offset + 0 );
	d1 = MBEDTLS_GET_UINT32_LE( input, offset + 4 );
	d2 = MBEDTLS_GET_UINT32_LE( input, offset + 8 );
	d3 = MBEDTLS_GET_UINT32_LE( input, offset + 12 );

	/* Compute: acc += (padded) block as a 130-bit integer */
	d0 += (uint64_t) acc0;
	d1 += (uint64_t) acc1 + ( d0 >> 32U );
	d2 += (uint64_t) acc2 + ( d1 >> 32U );
	d3 += (uint64_t) acc3 + ( d2 >> 32U );
	acc0 = (uint32_t) d0;
	acc1 = (uint32_t) d1;
	acc2 = (uint32_t) d2;
	acc3 = (uint32_t) d3;
	acc4 += (uint32_t) ( d3 >> 32U ) + needs_padding;

	/* Compute: acc = r /
	d0 = mul64( acc0, r0 ) +
	mul64( acc1, rs3 ) +
	mul64( acc2, rs2 ) +
	mul64( acc3, rs1 );
	d1 = mul64( acc0, r1 ) +
	mul64( acc1, r0 ) +
	mul64( acc2, rs3 ) +
	mul64( acc3, rs2 ) +
	mul64( acc4, rs1 );
	d2 = mul64( acc0, r2 ) +
	mul64( acc1, r1 ) +
	mul64( acc2, r0 ) +
	mul64( acc3, rs3 ) +
	mul64( acc4, rs2 );
	d3 = mul64( acc0, r3 ) +
	mul64( acc1, r2 ) +
	mul64( acc2, r1 ) +
	mul64( acc3, r0 ) +
	mul64( acc4, rs3 );
	acc4 *= r0;

	/* Compute: acc %= (2^130 - 5) (partial remainder) */
	d1 += ( d0 >> 32 );
	d2 += ( d1 >> 32 );
	d3 += ( d2 >> 32 );
	acc0 = (uint32_t) d0;
	acc1 = (uint32_t) d1;
	acc2 = (uint32_t) d2;
	acc3 = (uint32_t) d3;
	acc4 = (uint32_t) ( d3 >> 32 ) + acc4;

	d0 = (uint64_t) acc0 + ( acc4 >> 2 ) + ( acc4 & 0xFFFFFFFCU );
	acc4 &= 3U;
	acc0 = (uint32_t) d0;
	d0 = (uint64_t) acc1 + ( d0 >> 32U );
	acc1 = (uint32_t) d0;
	d0 = (uint64_t) acc2 + ( d0 >> 32U );
	acc2 = (uint32_t) d0;
	d0 = (uint64_t) acc3 + ( d0 >> 32U );
	acc3 = (uint32_t) d0;
	d0 = (uint64_t) acc4 + ( d0 >> 32U );
	acc4 = (uint32_t) d0;

	offset += POLY1305_BLOCK_SIZE_BYTES;
	}

	ctx->acc[0] = acc0;
	ctx->acc[1] = acc1;
	ctx->acc[2] = acc2;
	ctx->acc[3] = acc3;
	ctx->acc[4] = acc4;
	}

	/**
	* \brief Compute the Poly1305 MAC
	*
	* \param ctx The Poly1305 context.
	* \param mac The buffer to where the MAC is written. Must be
	* big enough to contain the 16-byte MAC.
	*/
	static void poly1305_compute_mac( const mbedtls_poly1305_context *ctx,
	unsigned char mac[16] )
	{
	uint64_t d;
	uint32_t g0, g1, g2, g3, g4;
	uint32_t acc0, acc1, acc2, acc3, acc4;
	uint32_t mask;
	uint32_t mask_inv;

	acc0 = ctx->acc[0];
	acc1 = ctx->acc[1];
	acc2 = ctx->acc[2];
	acc3 = ctx->acc[3];
	acc4 = ctx->acc[4];

	/* Before adding 's' we ensure that the accumulator is mod 2^130 - 5.
	* We do this by calculating acc - (2^130 - 5), then checking if
	* the 131st bit is set. If it is, then reduce: acc -= (2^130 - 5)
	*/

	/* Calculate acc + -(2^130 - 5) */
	d = ( (uint64_t) acc0 + 5U );
	g0 = (uint32_t) d;
	d = ( (uint64_t) acc1 + ( d >> 32 ) );
	g1 = (uint32_t) d;
	d = ( (uint64_t) acc2 + ( d >> 32 ) );
	g2 = (uint32_t) d;
	d = ( (uint64_t) acc3 + ( d >> 32 ) );
	g3 = (uint32_t) d;
	g4 = acc4 + (uint32_t) ( d >> 32U );

	/* mask == 0xFFFFFFFF if 131st bit is set, otherwise mask == 0 */
	mask = (uint32_t) 0U - ( g4 >> 2U );
	mask_inv = ~mask;

	/* If 131st bit is set then acc=g, otherwise, acc is unmodified */
	acc0 = ( acc0 & mask_inv ) \| ( g0 & mask );
	acc1 = ( acc1 & mask_inv ) \| ( g1 & mask );
	acc2 = ( acc2 & mask_inv ) \| ( g2 & mask );
	acc3 = ( acc3 & mask_inv ) \| ( g3 & mask );

	/* Add 's' */
	d = (uint64_t) acc0 + ctx->s[0];
	acc0 = (uint32_t) d;
	d = (uint64_t) acc1 + ctx->s[1] + ( d >> 32U );
	acc1 = (uint32_t) d;
	d = (uint64_t) acc2 + ctx->s[2] + ( d >> 32U );
	acc2 = (uint32_t) d;
	acc3 += ctx->s[3] + (uint32_t) ( d >> 32U );

	/* Compute MAC (128 least significant bits of the accumulator) */
	MBEDTLS_PUT_UINT32_LE( acc0, mac, 0 );
	MBEDTLS_PUT_UINT32_LE( acc1, mac, 4 );
	MBEDTLS_PUT_UINT32_LE( acc2, mac, 8 );
	MBEDTLS_PUT_UINT32_LE( acc3, mac, 12 );
	}

	void mbedtls_poly1305_init( mbedtls_poly1305_context *ctx )
	{
	POLY1305_VALIDATE( ctx != NULL );

	mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
	}

	void mbedtls_poly1305_free( mbedtls_poly1305_context *ctx )
	{
	if( ctx == NULL )
	return;

	mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
	}

	int mbedtls_poly1305_starts( mbedtls_poly1305_context *ctx,
	const unsigned char key[32] )
	{
	POLY1305_VALIDATE_RET( ctx != NULL );
	POLY1305_VALIDATE_RET( key != NULL );

	/* r &= 0x0ffffffc0ffffffc0ffffffc0fffffff */
	ctx->r[0] = MBEDTLS_GET_UINT32_LE( key, 0 ) & 0x0FFFFFFFU;
	ctx->r[1] = MBEDTLS_GET_UINT32_LE( key, 4 ) & 0x0FFFFFFCU;
	ctx->r[2] = MBEDTLS_GET_UINT32_LE( key, 8 ) & 0x0FFFFFFCU;
	ctx->r[3] = MBEDTLS_GET_UINT32_LE( key, 12 ) & 0x0FFFFFFCU;

	ctx->s[0] = MBEDTLS_GET_UINT32_LE( key, 16 );
	ctx->s[1] = MBEDTLS_GET_UINT32_LE( key, 20 );
	ctx->s[2] = MBEDTLS_GET_UINT32_LE( key, 24 );
	ctx->s[3] = MBEDTLS_GET_UINT32_LE( key, 28 );

	/* Initial accumulator state */
	ctx->acc[0] = 0U;
	ctx->acc[1] = 0U;
	ctx->acc[2] = 0U;
	ctx->acc[3] = 0U;
	ctx->acc[4] = 0U;

	/* Queue initially empty */
	mbedtls_platform_zeroize( ctx->queue, sizeof( ctx->queue ) );
	ctx->queue_len = 0U;

	return( 0 );
	}

	int mbedtls_poly1305_update( mbedtls_poly1305_context *ctx,
	const unsigned char *input,
	size_t ilen )
	{
	size_t offset = 0U;
	size_t remaining = ilen;
	size_t queue_free_len;
	size_t nblocks;
	POLY1305_VALIDATE_RET( ctx != NULL );
	POLY1305_VALIDATE_RET( ilen == 0 \|\| input != NULL );

	if( ( remaining > 0U ) && ( ctx->queue_len > 0U ) )
	{
	queue_free_len = ( POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );

	if( ilen < queue_free_len )
	{
	/* Not enough data to complete the block.
	* Store this data with the other leftovers.
	*/
	memcpy( &ctx->queue[ctx->queue_len],
	input,
	ilen );

	ctx->queue_len += ilen;

	remaining = 0U;
	}
	else
	{
	/* Enough data to produce a complete block */
	memcpy( &ctx->queue[ctx->queue_len],
	input,
	queue_free_len );

	ctx->queue_len = 0U;

	poly1305_process( ctx, 1U, ctx->queue, 1U ); /* add padding bit */

	offset += queue_free_len;
	remaining -= queue_free_len;
	}
	}

	if( remaining >= POLY1305_BLOCK_SIZE_BYTES )
	{
	nblocks = remaining / POLY1305_BLOCK_SIZE_BYTES;

	poly1305_process( ctx, nblocks, &input[offset], 1U );

	offset += nblocks * POLY1305_BLOCK_SIZE_BYTES;
	remaining %= POLY1305_BLOCK_SIZE_BYTES;
	}

	if( remaining > 0U )
	{
	/* Store partial block */
	ctx->queue_len = remaining;
	memcpy( ctx->queue, &input[offset], remaining );
	}

	return( 0 );
	}

	int mbedtls_poly1305_finish( mbedtls_poly1305_context *ctx,
	unsigned char mac[16] )
	{
	POLY1305_VALIDATE_RET( ctx != NULL );
	POLY1305_VALIDATE_RET( mac != NULL );

	/* Process any leftover data */
	if( ctx->queue_len > 0U )
	{
	/* Add padding bit */
	ctx->queue[ctx->queue_len] = 1U;
	ctx->queue_len++;

	/* Pad with zeroes */
	memset( &ctx->queue[ctx->queue_len],
	0,
	POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );

	poly1305_process( ctx, 1U, /* Process 1 block */
	ctx->queue, 0U ); /* Already padded above */
	}

	poly1305_compute_mac( ctx, mac );

	return( 0 );
	}

	int mbedtls_poly1305_mac( const unsigned char key[32],
	const unsigned char *input,
	size_t ilen,
	unsigned char mac[16] )
	{
	mbedtls_poly1305_context ctx;
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	POLY1305_VALIDATE_RET( key != NULL );
	POLY1305_VALIDATE_RET( mac != NULL );
	POLY1305_VALIDATE_RET( ilen == 0 \|\| input != NULL );

	mbedtls_poly1305_init( &ctx );

	ret = mbedtls_poly1305_starts( &ctx, key );
	if( ret != 0 )
	goto cleanup;

	ret = mbedtls_poly1305_update( &ctx, input, ilen );
	if( ret != 0 )
	goto cleanup;

	ret = mbedtls_poly1305_finish( &ctx, mac );

	cleanup:
	mbedtls_poly1305_free( &ctx );
	return( ret );
	}

	#endif /* MBEDTLS_POLY1305_ALT */

	#if defined(MBEDTLS_SELF_TEST)

	static const unsigned char test_keys[2][32] =
	{
	{
	0x85, 0xd6, 0xbe, 0x78, 0x57, 0x55, 0x6d, 0x33,
	0x7f, 0x44, 0x52, 0xfe, 0x42, 0xd5, 0x06, 0xa8,
	0x01, 0x03, 0x80, 0x8a, 0xfb, 0x0d, 0xb2, 0xfd,
	0x4a, 0xbf, 0xf6, 0xaf, 0x41, 0x49, 0xf5, 0x1b
	},
	{
	0x1c, 0x92, 0x40, 0xa5, 0xeb, 0x55, 0xd3, 0x8a,
	0xf3, 0x33, 0x88, 0x86, 0x04, 0xf6, 0xb5, 0xf0,
	0x47, 0x39, 0x17, 0xc1, 0x40, 0x2b, 0x80, 0x09,
	0x9d, 0xca, 0x5c, 0xbc, 0x20, 0x70, 0x75, 0xc0
	}
	};

	static const unsigned char test_data[2][127] =
	{
	{
	0x43, 0x72, 0x79, 0x70, 0x74, 0x6f, 0x67, 0x72,
	0x61, 0x70, 0x68, 0x69, 0x63, 0x20, 0x46, 0x6f,
	0x72, 0x75, 0x6d, 0x20, 0x52, 0x65, 0x73, 0x65,
	0x61, 0x72, 0x63, 0x68, 0x20, 0x47, 0x72, 0x6f,
	0x75, 0x70
	},
	{
	0x27, 0x54, 0x77, 0x61, 0x73, 0x20, 0x62, 0x72,
	0x69, 0x6c, 0x6c, 0x69, 0x67, 0x2c, 0x20, 0x61,
	0x6e, 0x64, 0x20, 0x74, 0x68, 0x65, 0x20, 0x73,
	0x6c, 0x69, 0x74, 0x68, 0x79, 0x20, 0x74, 0x6f,
	0x76, 0x65, 0x73, 0x0a, 0x44, 0x69, 0x64, 0x20,
	0x67, 0x79, 0x72, 0x65, 0x20, 0x61, 0x6e, 0x64,
	0x20, 0x67, 0x69, 0x6d, 0x62, 0x6c, 0x65, 0x20,
	0x69, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x77,
	0x61, 0x62, 0x65, 0x3a, 0x0a, 0x41, 0x6c, 0x6c,
	0x20, 0x6d, 0x69, 0x6d, 0x73, 0x79, 0x20, 0x77,
	0x65, 0x72, 0x65, 0x20, 0x74, 0x68, 0x65, 0x20,
	0x62, 0x6f, 0x72, 0x6f, 0x67, 0x6f, 0x76, 0x65,
	0x73, 0x2c, 0x0a, 0x41, 0x6e, 0x64, 0x20, 0x74,
	0x68, 0x65, 0x20, 0x6d, 0x6f, 0x6d, 0x65, 0x20,
	0x72, 0x61, 0x74, 0x68, 0x73, 0x20, 0x6f, 0x75,
	0x74, 0x67, 0x72, 0x61, 0x62, 0x65, 0x2e
	}
	};

	static const size_t test_data_len[2] =
	{
	34U,
	127U
	};

	static const unsigned char test_mac[2][16] =
	{
	{
	0xa8, 0x06, 0x1d, 0xc1, 0x30, 0x51, 0x36, 0xc6,
	0xc2, 0x2b, 0x8b, 0xaf, 0x0c, 0x01, 0x27, 0xa9
	},
	{
	0x45, 0x41, 0x66, 0x9a, 0x7e, 0xaa, 0xee, 0x61,
	0xe7, 0x08, 0xdc, 0x7c, 0xbc, 0xc5, 0xeb, 0x62
	}
	};

	/* Make sure no other definition is already present. */
	#undef ASSERT

	#define ASSERT( cond, args ) \
	do \
	{ \
	if( ! ( cond ) ) \
	{ \
	if( verbose != 0 ) \
	mbedtls_printf args; \
	\
	return( -1 ); \
	} \
	} \
	while( 0 )

	int mbedtls_poly1305_self_test( int verbose )
	{
	unsigned char mac[16];
	unsigned i;
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	for( i = 0U; i < 2U; i++ )
	{
	if( verbose != 0 )
	mbedtls_printf( " Poly1305 test %u ", i );

	ret = mbedtls_poly1305_mac( test_keys[i],
	test_data[i],
	test_data_len[i],
	mac );
	ASSERT( 0 == ret, ( "error code: %i\n", ret ) );

	ASSERT( 0 == memcmp( mac, test_mac[i], 16U ), ( "failed (mac)\n" ) );

	if( verbose != 0 )
	mbedtls_printf( "passed\n" );
	}

	if( verbose != 0 )
	mbedtls_printf( "\n" );

	return( 0 );
	}

	#endif /* MBEDTLS_SELF_TEST */

	#endif /* MBEDTLS_POLY1305_C */