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234 lines
10 KiB
C
234 lines
10 KiB
C
/*
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---------------------------------------------------------------------------
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Copyright (c) 1998-2010, Brian Gladman, Worcester, UK. All rights reserved.
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The redistribution and use of this software (with or without changes)
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is allowed without the payment of fees or royalties provided that:
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source code distributions include the above copyright notice, this
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list of conditions and the following disclaimer;
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binary distributions include the above copyright notice, this list
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of conditions and the following disclaimer in their documentation.
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This software is provided 'as is' with no explicit or implied warranties
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in respect of its operation, including, but not limited to, correctness
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and fitness for purpose.
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---------------------------------------------------------------------------
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Issue Date: 11/01/2011
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I am grateful for the work done by Mark Rodenkirch and Jason Papadopoulos
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in helping to remove a bug in the operation of this code on big endian
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systems when fast buffer operations are enabled.
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---------------------------------------------------------------------------
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*/
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#ifndef _GCM_H
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#define _GCM_H
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#include "aes.h"
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#include "gf128mul.h"
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/* USER DEFINABLE OPTIONS (Further options need to be set in gf128mul.h) */
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/* UNIT_BITS sets the size of variables used to process 16 byte buffers
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when the buffer alignment allows this. When buffers are processed
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in bytes, 16 individual operations are invoolved. But if, say, such
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a buffer is divided into 4 32 bit variables, it can then be processed
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in 4 operations, making the code typically much faster. In general
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it will pay to use the longest natively supported size, which will
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probably be 32 or 64 bits in 32 and 64 bit systems respectively.
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*/
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#if defined( UNIT_BITS )
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# undef UNIT_BITS
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#endif
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#if !defined( UNIT_BITS )
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# if PLATFORM_BYTE_ORDER == IS_BIG_ENDIAN
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# if 0
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# define UNIT_BITS 8
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# elif 0
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# define UNIT_BITS 32
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# elif 1
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# define UNIT_BITS 64
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# endif
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# elif defined( _WIN64 )
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# define UNIT_BITS 64
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# else
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# define UNIT_BITS 32
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# endif
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#endif
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#if UNIT_BITS == 64 && !defined( NEED_UINT_64T )
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# define NEED_UINT_64T
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#endif
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/* END OF USER DEFINABLE OPTIONS */
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/* After encryption or decryption operations the return value of
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'compute tag' will be one of the values RETURN_GOOD, RETURN_WARN
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or RETURN_ERROR, the latter indicating an error. A return value
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RETURN_GOOD indicates that both encryption and authentication
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have taken place and resulted in the returned tag value. If
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the returned value is RETURN_WARN, the tag value is the result
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of authentication alone without encryption (CCM) or decryption
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(GCM and EAX).
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*/
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#ifndef RETURN_GOOD
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# define RETURN_WARN 1
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# define RETURN_GOOD 0
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# define RETURN_ERROR -1
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#endif
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#if defined(__cplusplus)
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extern "C"
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{
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#endif
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#ifndef RET_TYPE_DEFINED
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typedef int ret_type;
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#endif
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UNIT_TYPEDEF(gcm_unit_t, UNIT_BITS);
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BUFR_TYPEDEF(gcm_buf_t, UNIT_BITS, AES_BLOCK_SIZE);
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#define GCM_BLOCK_SIZE AES_BLOCK_SIZE
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/* The GCM-AES context */
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typedef struct
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{
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#if defined( TABLES_64K )
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gf_t64k_a gf_t64k;
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#endif
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#if defined( TABLES_8K )
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gf_t8k_a gf_t8k;
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#endif
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#if defined( TABLES_4K )
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gf_t4k_a gf_t4k;
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#endif
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#if defined( TABLES_256 )
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gf_t256_a gf_t256;
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#endif
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gcm_buf_t ctr_val; /* CTR counter value */
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gcm_buf_t enc_ctr; /* encrypted CTR block */
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gcm_buf_t hdr_ghv; /* ghash buffer (header) */
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gcm_buf_t txt_ghv; /* ghash buffer (ciphertext) */
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gf_t ghash_h; /* ghash H value */
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aes_encrypt_ctx aes[1]; /* AES encryption context */
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uint32_t y0_val; /* initial counter value */
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uint32_t hdr_cnt; /* header bytes so far */
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uint32_t txt_ccnt; /* text bytes so far (encrypt) */
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uint32_t txt_acnt; /* text bytes so far (auth) */
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} gcm_ctx;
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/* The following calls handle mode initialisation, keying and completion */
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ret_type gcm_init_and_key( /* initialise mode and set key */
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const unsigned char key[], /* the key value */
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unsigned long key_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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ret_type gcm_end( /* clean up and end operation */
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gcm_ctx ctx[1]); /* the mode context */
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/* The following calls handle complete messages in memory as one operation */
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ret_type gcm_encrypt_message( /* encrypt an entire message */
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const unsigned char iv[], /* the initialisation vector */
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unsigned long iv_len, /* and its length in bytes */
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const unsigned char hdr[], /* the header buffer */
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unsigned long hdr_len, /* and its length in bytes */
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unsigned char msg[], /* the message buffer */
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unsigned long msg_len, /* and its length in bytes */
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unsigned char tag[], /* the buffer for the tag */
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unsigned long tag_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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/* RETURN_GOOD is returned if the input tag */
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/* matches that for the decrypted message */
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ret_type gcm_decrypt_message( /* decrypt an entire message */
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const unsigned char iv[], /* the initialisation vector */
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unsigned long iv_len, /* and its length in bytes */
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const unsigned char hdr[], /* the header buffer */
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unsigned long hdr_len, /* and its length in bytes */
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unsigned char msg[], /* the message buffer */
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unsigned long msg_len, /* and its length in bytes */
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const unsigned char tag[], /* the buffer for the tag */
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unsigned long tag_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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/* The following calls handle messages in a sequence of operations followed */
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/* by tag computation after the sequence has been completed. In these calls */
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/* the user is responsible for verfiying the computed tag on decryption */
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ret_type gcm_init_message( /* initialise a new message */
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const unsigned char iv[], /* the initialisation vector */
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unsigned long iv_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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ret_type gcm_auth_header( /* authenticate the header */
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const unsigned char hdr[], /* the header buffer */
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unsigned long hdr_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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ret_type gcm_encrypt( /* encrypt & authenticate data */
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unsigned char data[], /* the data buffer */
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unsigned long data_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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ret_type gcm_decrypt( /* authenticate & decrypt data */
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unsigned char data[], /* the data buffer */
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unsigned long data_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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ret_type gcm_compute_tag( /* compute authentication tag */
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unsigned char tag[], /* the buffer for the tag */
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unsigned long tag_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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/* The use of the following calls should be avoided if possible because
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their use requires a very good understanding of the way this encryption
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mode works and the way in which this code implements it in order to use
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them correctly.
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The gcm_auth_data routine is used to authenticate encrypted message data.
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In message encryption gcm_crypt_data must be called before gcm_auth_data
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is called since it is encrypted data that is authenticated. In message
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decryption authentication must occur before decryption and data can be
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authenticated without being decrypted if necessary.
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If these calls are used it is up to the user to ensure that these routines
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are called in the correct order and that the correct data is passed to
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them.
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When gcm_compute_tag is called it is assumed that an error in use has
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occurred if both encryption (or decryption) and authentication have taken
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place but the total lengths of the message data respectively authenticated
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and encrypted are not the same. If authentication has taken place but
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there has been no corresponding encryption or decryption operations (none
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at all) only a warning is issued. This should be treated as an error if it
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occurs during encryption but it is only signalled as a warning as it might
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be intentional when decryption operations are involved (this avoids having
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different compute tag functions for encryption and decryption). Decryption
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operations can be undertaken freely after authetication but if the tag is
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computed after such operations an error will be signalled if the lengths
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of the data authenticated and decrypted don't match.
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*/
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ret_type gcm_auth_data( /* authenticate ciphertext data */
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const unsigned char data[], /* the data buffer */
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unsigned long data_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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ret_type gcm_crypt_data( /* encrypt or decrypt data */
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unsigned char data[], /* the data buffer */
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unsigned long data_len, /* and its length in bytes */
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gcm_ctx ctx[1]); /* the mode context */
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#if defined(__cplusplus)
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}
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#endif
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#endif
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