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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" EVP_PKEY_decrypt_init, EVP_PKEY_decrypt \- decrypt using a public key algorithm .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/evp.h> \& \& int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx); \& int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx, \& unsigned char *out, size_t *outlen, \& const unsigned char *in, size_t inlen); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" The \fBEVP_PKEY_decrypt_init()\fR function initializes a public key algorithm context using key \fBpkey\fR for a decryption operation. .PP The \fBEVP_PKEY_decrypt()\fR function performs a public key decryption operation using \fBctx\fR. The data to be decrypted is specified using the \fBin\fR and \&\fBinlen\fR parameters. If \fBout\fR is \fB\s-1NULL\s0\fR then the maximum size of the output buffer is written to the \fBoutlen\fR parameter. If \fBout\fR is not \fB\s-1NULL\s0\fR then before the call the \fBoutlen\fR parameter should contain the length of the \&\fBout\fR buffer, if the call is successful the decrypted data is written to \&\fBout\fR and the amount of data written to \fBoutlen\fR. .SH "NOTES" .IX Header "NOTES" After the call to \fBEVP_PKEY_decrypt_init()\fR algorithm specific control operations can be performed to set any appropriate parameters for the operation. .PP The function \fBEVP_PKEY_decrypt()\fR can be called more than once on the same context if several operations are performed using the same parameters. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBEVP_PKEY_decrypt_init()\fR and \fBEVP_PKEY_decrypt()\fR return 1 for success and 0 or a negative value for failure. In particular a return value of \-2 indicates the operation is not supported by the public key algorithm. .SH "EXAMPLES" .IX Header "EXAMPLES" Decrypt data using \s-1OAEP\s0 (for \s-1RSA\s0 keys): .PP .Vb 2 \& #include <openssl/evp.h> \& #include <openssl/rsa.h> \& \& EVP_PKEY_CTX *ctx; \& ENGINE *eng; \& unsigned char *out, *in; \& size_t outlen, inlen; \& EVP_PKEY *key; \& \& /* \& * NB: assumes key, eng, in, inlen are already set up \& * and that key is an RSA private key \& */ \& ctx = EVP_PKEY_CTX_new(key, eng); \& if (!ctx) \& /* Error occurred */ \& if (EVP_PKEY_decrypt_init(ctx) <= 0) \& /* Error */ \& if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0) \& /* Error */ \& \& /* Determine buffer length */ \& if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0) \& /* Error */ \& \& out = OPENSSL_malloc(outlen); \& \& if (!out) \& /* malloc failure */ \& \& if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0) \& /* Error */ \& \& /* Decrypted data is outlen bytes written to buffer out */ .Ve .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBEVP_PKEY_CTX_new\fR\|(3), \&\fBEVP_PKEY_encrypt\fR\|(3), \&\fBEVP_PKEY_sign\fR\|(3), \&\fBEVP_PKEY_verify\fR\|(3), \&\fBEVP_PKEY_verify_recover\fR\|(3), \&\fBEVP_PKEY_derive\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" These functions were added in OpenSSL 1.0.0. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2006\-2019 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.