EVP_PKEY_decrypt.pod 2.9 KB

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  1. =pod
  2. =head1 NAME
  3. EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public key algorithm
  4. =head1 SYNOPSIS
  5. #include <openssl/evp.h>
  6. int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
  7. int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx,
  8. unsigned char *out, size_t *outlen,
  9. const unsigned char *in, size_t inlen);
  10. =head1 DESCRIPTION
  11. The EVP_PKEY_decrypt_init() function initializes a public key algorithm
  12. context using key B<pkey> for a decryption operation.
  13. The EVP_PKEY_decrypt() function performs a public key decryption operation
  14. using B<ctx>. The data to be decrypted is specified using the B<in> and
  15. B<inlen> parameters. If B<out> is B<NULL> then the maximum size of the output
  16. buffer is written to the B<outlen> parameter. If B<out> is not B<NULL> then
  17. before the call the B<outlen> parameter should contain the length of the
  18. B<out> buffer, if the call is successful the decrypted data is written to
  19. B<out> and the amount of data written to B<outlen>.
  20. =head1 NOTES
  21. After the call to EVP_PKEY_decrypt_init() algorithm specific control
  22. operations can be performed to set any appropriate parameters for the
  23. operation.
  24. The function EVP_PKEY_decrypt() can be called more than once on the same
  25. context if several operations are performed using the same parameters.
  26. =head1 RETURN VALUES
  27. EVP_PKEY_decrypt_init() and EVP_PKEY_decrypt() return 1 for success and 0
  28. or a negative value for failure. In particular a return value of -2
  29. indicates the operation is not supported by the public key algorithm.
  30. =head1 EXAMPLES
  31. Decrypt data using OAEP (for RSA keys):
  32. #include <openssl/evp.h>
  33. #include <openssl/rsa.h>
  34. EVP_PKEY_CTX *ctx;
  35. ENGINE *eng;
  36. unsigned char *out, *in;
  37. size_t outlen, inlen;
  38. EVP_PKEY *key;
  39. /*
  40. * NB: assumes key, eng, in, inlen are already set up
  41. * and that key is an RSA private key
  42. */
  43. ctx = EVP_PKEY_CTX_new(key, eng);
  44. if (!ctx)
  45. /* Error occurred */
  46. if (EVP_PKEY_decrypt_init(ctx) <= 0)
  47. /* Error */
  48. if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0)
  49. /* Error */
  50. /* Determine buffer length */
  51. if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0)
  52. /* Error */
  53. out = OPENSSL_malloc(outlen);
  54. if (!out)
  55. /* malloc failure */
  56. if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0)
  57. /* Error */
  58. /* Decrypted data is outlen bytes written to buffer out */
  59. =head1 SEE ALSO
  60. L<EVP_PKEY_CTX_new(3)>,
  61. L<EVP_PKEY_encrypt(3)>,
  62. L<EVP_PKEY_sign(3)>,
  63. L<EVP_PKEY_verify(3)>,
  64. L<EVP_PKEY_verify_recover(3)>,
  65. L<EVP_PKEY_derive(3)>
  66. =head1 HISTORY
  67. These functions were added in OpenSSL 1.0.0.
  68. =head1 COPYRIGHT
  69. Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved.
  70. Licensed under the Apache License 2.0 (the "License"). You may not use
  71. this file except in compliance with the License. You can obtain a copy
  72. in the file LICENSE in the source distribution or at
  73. L<https://www.openssl.org/source/license.html>.
  74. =cut