1EVP_PKEY_VERIFY_RECOVER(3) OpenSSL EVP_PKEY_VERIFY_RECOVER(3)
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6 EVP_PKEY_verify_recover_init, EVP_PKEY_verify_recover - recover
7 signature using a public key algorithm
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10 #include <openssl/evp.h>
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12 int EVP_PKEY_verify_recover_init(EVP_PKEY_CTX *ctx);
13 int EVP_PKEY_verify_recover(EVP_PKEY_CTX *ctx,
14 unsigned char *rout, size_t *routlen,
15 const unsigned char *sig, size_t siglen);
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18 The EVP_PKEY_verify_recover_init() function initializes a public key
19 algorithm context using key pkey for a verify recover operation.
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21 The EVP_PKEY_verify_recover() function recovers signed data using ctx.
22 The signature is specified using the sig and siglen parameters. If rout
23 is NULL then the maximum size of the output buffer is written to the
24 routlen parameter. If rout is not NULL then before the call the routlen
25 parameter should contain the length of the rout buffer, if the call is
26 successful recovered data is written to rout and the amount of data
27 written to routlen.
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30 Normally an application is only interested in whether a signature
31 verification operation is successful in those cases the EVP_verify()
32 function should be used.
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34 Sometimes however it is useful to obtain the data originally signed
35 using a signing operation. Only certain public key algorithms can
36 recover a signature in this way (for example RSA in PKCS padding mode).
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38 After the call to EVP_PKEY_verify_recover_init() algorithm specific
39 control operations can be performed to set any appropriate parameters
40 for the operation.
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42 The function EVP_PKEY_verify_recover() can be called more than once on
43 the same context if several operations are performed using the same
44 parameters.
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47 EVP_PKEY_verify_recover_init() and EVP_PKEY_verify_recover() return 1
48 for success and 0 or a negative value for failure. In particular a
49 return value of -2 indicates the operation is not supported by the
50 public key algorithm.
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53 Recover digest originally signed using PKCS#1 and SHA256 digest:
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55 #include <openssl/evp.h>
56 #include <openssl/rsa.h>
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58 EVP_PKEY_CTX *ctx;
59 unsigned char *rout, *sig;
60 size_t routlen, siglen;
61 EVP_PKEY *verify_key;
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63 /*
64 * NB: assumes verify_key, sig and siglen are already set up
65 * and that verify_key is an RSA public key
66 */
67 ctx = EVP_PKEY_CTX_new(verify_key, NULL /* no engine */);
68 if (!ctx)
69 /* Error occurred */
70 if (EVP_PKEY_verify_recover_init(ctx) <= 0)
71 /* Error */
72 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
73 /* Error */
74 if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
75 /* Error */
76
77 /* Determine buffer length */
78 if (EVP_PKEY_verify_recover(ctx, NULL, &routlen, sig, siglen) <= 0)
79 /* Error */
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81 rout = OPENSSL_malloc(routlen);
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83 if (!rout)
84 /* malloc failure */
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86 if (EVP_PKEY_verify_recover(ctx, rout, &routlen, sig, siglen) <= 0)
87 /* Error */
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89 /* Recovered data is routlen bytes written to buffer rout */
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92 EVP_PKEY_CTX_new(3), EVP_PKEY_encrypt(3), EVP_PKEY_decrypt(3),
93 EVP_PKEY_sign(3), EVP_PKEY_verify(3), EVP_PKEY_derive(3)
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96 These functions were added in OpenSSL 1.0.0.
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99 Copyright 2013-2019 The OpenSSL Project Authors. All Rights Reserved.
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101 Licensed under the OpenSSL license (the "License"). You may not use
102 this file except in compliance with the License. You can obtain a copy
103 in the file LICENSE in the source distribution or at
104 <https://www.openssl.org/source/license.html>.
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1081.1.1i 2021-01-26 EVP_PKEY_VERIFY_RECOVER(3)