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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" RSA_private_encrypt, RSA_public_decrypt \- low\-level signature operations .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/rsa.h> \& \& int RSA_private_encrypt(int flen, unsigned char *from, \& unsigned char *to, RSA *rsa, int padding); \& \& int RSA_public_decrypt(int flen, unsigned char *from, \& unsigned char *to, RSA *rsa, int padding); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" These functions handle \s-1RSA\s0 signatures at a low-level. .PP \&\fBRSA_private_encrypt()\fR signs the \fBflen\fR bytes at \fBfrom\fR (usually a message digest with an algorithm identifier) using the private key \&\fBrsa\fR and stores the signature in \fBto\fR. \fBto\fR must point to \&\fBRSA_size(rsa)\fR bytes of memory. .PP \&\fBpadding\fR denotes one of the following modes: .IP "\s-1RSA_PKCS1_PADDING\s0" 4 .IX Item "RSA_PKCS1_PADDING" \&\s-1PKCS\s0 #1 v1.5 padding. This function does not handle the \&\fBalgorithmIdentifier\fR specified in \s-1PKCS\s0 #1. When generating or verifying \s-1PKCS\s0 #1 signatures, \fBRSA_sign\fR\|(3) and \fBRSA_verify\fR\|(3) should be used. .IP "\s-1RSA_NO_PADDING\s0" 4 .IX Item "RSA_NO_PADDING" Raw \s-1RSA\s0 signature. This mode should \fIonly\fR be used to implement cryptographically sound padding modes in the application code. Signing user data directly with \s-1RSA\s0 is insecure. .PP \&\fBRSA_public_decrypt()\fR recovers the message digest from the \fBflen\fR bytes long signature at \fBfrom\fR using the signer's public key \&\fBrsa\fR. \fBto\fR must point to a memory section large enough to hold the message digest (which is smaller than \fBRSA_size(rsa) \- 11\fR). \fBpadding\fR is the padding mode that was used to sign the data. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBRSA_private_encrypt()\fR returns the size of the signature (i.e., RSA_size(rsa)). \fBRSA_public_decrypt()\fR returns the size of the recovered message digest. .PP On error, \-1 is returned; the error codes can be obtained by \fBERR_get_error\fR\|(3). .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBERR_get_error\fR\|(3), \&\fBRSA_sign\fR\|(3), \fBRSA_verify\fR\|(3) .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2000\-2020 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>.