Evp_encryptinit_ex Example

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EVPEncryptInitex iv EVPEncryptInitex iv Since the iv token is reused, Anselm constrains its search to only match functions which contain the same Value pointer at that argument position. I also defined a syntax to perform negative lookaheads, which tells Anselm to look for the absence of specific function calls. May 29, 2020 EVPEncryptInitex iv EVPEncryptInitex iv Since the iv token is reused, Anselm constrains its search to only match functions which contain the same Value pointer at that argument position. I also defined a syntax to perform negative lookaheads, which tells Anselm to look for the absence of specific function calls. An example of AAD is the IP address and port number in a IP header used with IPsec. The output from the encryption operation will be the ciphertext, and a tag. The tag is subsequently used during the decryption operation to ensure that the ciphertext and AAD have not been tampered with. Jan 05, 2021 EVPEncryptInitex sets up the cipher context ctx for encryption with cipher type from ENGINE impl. If ctx points to an unused object on the stack, it must be initialized with EVPMDCTXinit before calling this function. Type is normally supplied by a function such as EVPaes256cbc (3).

Jan 21st, 2013
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Openssl aes evp
  1. AES encryption/decryption demo program using OpenSSL EVP apis
  2. **/
  3. #include <string.h>
  4. #include <stdlib.h>
  5. #define AES_BLOCK_SIZE 256
  6. /**
  7. * Create an 256 bit key and IV using the supplied key_data. salt can be added for taste.
  8. * Fills in the encryption and decryption ctx objects and returns 0 on success
  9. int aes_init(unsignedchar*key_data,int key_data_len,unsignedchar*salt, EVP_CIPHER_CTX *e_ctx,
  10. {
  11. unsignedchar key[32], iv[32];
  12. /*
  13. * Gen key & IV for AES 256 CBC mode. A SHA1 digest is used to hash the supplied key material.
  14. * nrounds is the number of times the we hash the material. More rounds are more secure but
  15. */
  16. i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt, key_data, key_data_len, nrounds, key, iv);
  17. printf('Key size is %d bits - should be 256 bitsn', i);
  18. }
  19. for(int x =0; x<32;++x)
  20. printf('salt: %xn', salt[x]);
  21. EVP_CIPHER_CTX_init(e_ctx);
  22. EVP_EncryptInit_ex(e_ctx, EVP_aes_256_cbc(), NULL, key, iv);
  23. EVP_DecryptInit_ex(d_ctx, EVP_aes_256_cbc(), NULL, key, iv);
  24. return0;
  25. * Encrypt *len bytes of data
  26. * All data going in & out is considered binary (unsigned char[])
  27. unsignedchar*aes_encrypt(EVP_CIPHER_CTX *e,unsignedchar*plaintext,int*len)
  28. /* max ciphertext len for a n bytes of plaintext is n + AES_BLOCK_SIZE -1 bytes */
  29. unsignedchar*ciphertext =(unsignedchar*)malloc(c_len);
  30. /* allows reusing of 'e' for multiple encryption cycles */
  31. if(!EVP_EncryptInit_ex(e, NULL, NULL, NULL, NULL)){
  32. return NULL;
  33. /* update ciphertext, c_len is filled with the length of ciphertext generated,
  34. if(!EVP_EncryptUpdate(e, ciphertext,&c_len, plaintext,*len)){
  35. return NULL;
  36. /* update ciphertext with the final remaining bytes */
  37. if(!EVP_EncryptFinal_ex(e, ciphertext+c_len,&f_len)){
  38. return NULL;
  39. return ciphertext;
  40. * Decrypt *len bytes of ciphertext
  41. unsignedchar*aes_decrypt(EVP_CIPHER_CTX *e,unsignedchar*ciphertext,int*len)
  42. /* plaintext will always be equal to or lesser than length of ciphertext*/
  43. unsignedchar*plaintext =(unsignedchar*)malloc(p_len);
  44. if(!EVP_DecryptInit_ex(e, NULL, NULL, NULL, NULL)){
  45. return NULL;
  46. if(!EVP_DecryptUpdate(e, plaintext,&p_len, ciphertext,*len)){
  47. return NULL;
  48. if(!EVP_DecryptFinal_ex(e, plaintext+p_len,&f_len)){
  49. return NULL;
  50. return plaintext;
  51. {
  52. /* 'opaque' encryption, decryption ctx structures that libcrypto uses to record
  53. EVP_CIPHER_CTX en, de;
  54. /* The salt paramter is used as a salt in the derivation: it should point to an 8 byte buffer or NULL if no salt is used. */
  55. int key_data_len, i;
  56. char*input[]={'a','abcd','this is a test','this is a bigger test',
  57. 'nWho are fyou ?nI am the 'Doctor'.n'Doctor' who ?nPrecisely!',
  58. NULL};
  59. /* the key_data is read from the argument list */
  60. key_data_len =strlen(argv[1]);
  61. /* gen key and iv. init the cipher ctx object */
  62. if(aes_init(key_data, key_data_len, salt,&en,&de)){
  63. return-1;
  64. /* encrypt and decrypt each input string and compare with the original */
  65. char*plaintext;
  66. int olen, len;
  67. /* The enc/dec functions deal with binary data and not C strings. strlen() will
  68. return length of the string without counting the '0' string marker. We always
  69. pass in the marker byte to the encrypt/decrypt functions so that after decryption
  70. olen = len =strlen(input[i])+1;
  71. ciphertext = aes_encrypt(&en,(unsignedchar*)input[i],&len);
  72. plaintext =(char*)aes_decrypt(&de, ciphertext,&len);
  73. if(strncmp(plaintext, input[i], olen))
  74. printf('FAIL: enc/dec failed for '%s'n', input[i]);
  75. printf('OK: enc/dec ok for '%s'n', plaintext);// '%s'n
  76. free(ciphertext);
  77. }
  78. EVP_CIPHER_CTX_cleanup(&de);
  79. }
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