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annotate libtomcrypt/src/encauth/ocb3/ocb3_decrypt.c @ 1659:d32bcb5c557d

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Add Ed25519 support (#91) * Add support for Ed25519 as a public key type Ed25519 is a elliptic curve signature scheme that offers better security than ECDSA and DSA and good performance. It may be used for both user and host keys. OpenSSH key import and fuzzer are not supported yet. Initially inspired by Peter Szabo. * Add curve25519 and ed25519 fuzzers * Add import and export of Ed25519 keys
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Wed, 11 Mar 2020 21:09:45 +0500
parents 6dba84798cd5
children
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rev   line source
1471
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9
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10 /**
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11 @file ocb3_decrypt.c
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12 OCB implementation, decrypt data, by Tom St Denis
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13 */
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14 #include "tomcrypt.h"
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15
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16 #ifdef LTC_OCB3_MODE
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17
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18 /**
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19 Decrypt blocks of ciphertext with OCB
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20 @param ocb The OCB state
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21 @param ct The ciphertext (length multiple of the block size of the block cipher)
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22 @param ctlen The length of the input (octets)
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23 @param pt [out] The plaintext (length of ct)
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24 @return CRYPT_OK if successful
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25 */
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26 int ocb3_decrypt(ocb3_state *ocb, const unsigned char *ct, unsigned long ctlen, unsigned char *pt)
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27 {
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28 unsigned char tmp[MAXBLOCKSIZE];
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29 int err, i, full_blocks;
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30 unsigned char *pt_b, *ct_b;
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31
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32 LTC_ARGCHK(ocb != NULL);
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33 if (ctlen == 0) return CRYPT_OK; /* no data, nothing to do */
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34 LTC_ARGCHK(ct != NULL);
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35 LTC_ARGCHK(pt != NULL);
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36
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37 if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
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38 return err;
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39 }
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40 if (ocb->block_len != cipher_descriptor[ocb->cipher].block_length) {
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41 return CRYPT_INVALID_ARG;
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42 }
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43
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44 if (ctlen % ocb->block_len) { /* ctlen has to bu multiple of block_len */
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45 return CRYPT_INVALID_ARG;
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46 }
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47
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48 full_blocks = ctlen/ocb->block_len;
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49 for(i=0; i<full_blocks; i++) {
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50 pt_b = (unsigned char *)pt+i*ocb->block_len;
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51 ct_b = (unsigned char *)ct+i*ocb->block_len;
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52
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53 /* ocb->Offset_current[] = ocb->Offset_current[] ^ Offset_{ntz(block_index)} */
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54 ocb3_int_xor_blocks(ocb->Offset_current, ocb->Offset_current, ocb->L_[ocb3_int_ntz(ocb->block_index)], ocb->block_len);
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55
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56 /* tmp[] = ct[] XOR ocb->Offset_current[] */
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57 ocb3_int_xor_blocks(tmp, ct_b, ocb->Offset_current, ocb->block_len);
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58
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59 /* decrypt */
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60 if ((err = cipher_descriptor[ocb->cipher].ecb_decrypt(tmp, tmp, &ocb->key)) != CRYPT_OK) {
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61 goto LBL_ERR;
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62 }
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63
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64 /* pt[] = tmp[] XOR ocb->Offset_current[] */
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65 ocb3_int_xor_blocks(pt_b, tmp, ocb->Offset_current, ocb->block_len);
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66
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67 /* ocb->checksum[] = ocb->checksum[] XOR pt[] */
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68 ocb3_int_xor_blocks(ocb->checksum, ocb->checksum, pt_b, ocb->block_len);
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69
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70 ocb->block_index++;
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71 }
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72
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73 err = CRYPT_OK;
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74
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75 LBL_ERR:
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76 #ifdef LTC_CLEAN_STACK
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77 zeromem(tmp, sizeof(tmp));
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78 #endif
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79 return err;
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80 }
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81
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82 #endif
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83
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84 /* ref: $Format:%D$ */
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85 /* git commit: $Format:%H$ */
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86 /* commit time: $Format:%ai$ */