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Editing: RSA_private_decrypt.3
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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_public_encrypt, RSA_private_decrypt \- RSA public key cryptography .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/rsa.h> \& \& int RSA_public_encrypt(int flen, const unsigned char *from, \& unsigned char *to, RSA *rsa, int padding); \& \& int RSA_private_decrypt(int flen, const unsigned char *from, \& unsigned char *to, RSA *rsa, int padding); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fBRSA_public_encrypt()\fR encrypts the \fBflen\fR bytes at \fBfrom\fR (usually a session key) using the public key \fBrsa\fR and stores the ciphertext in \&\fBto\fR. \fBto\fR must point to RSA_size(\fBrsa\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 currently is the most widely used mode. .IP "\s-1RSA_PKCS1_OAEP_PADDING\s0" 4 .IX Item "RSA_PKCS1_OAEP_PADDING" EME-OAEP as defined in \s-1PKCS\s0 #1 v2.0 with \s-1SHA\-1, MGF1\s0 and an empty encoding parameter. This mode is recommended for all new applications. .IP "\s-1RSA_SSLV23_PADDING\s0" 4 .IX Item "RSA_SSLV23_PADDING" \&\s-1PKCS\s0 #1 v1.5 padding with an SSL-specific modification that denotes that the server is \s-1SSL3\s0 capable. .IP "\s-1RSA_NO_PADDING\s0" 4 .IX Item "RSA_NO_PADDING" Raw \s-1RSA\s0 encryption. This mode should \fIonly\fR be used to implement cryptographically sound padding modes in the application code. Encrypting user data directly with \s-1RSA\s0 is insecure. .PP \&\fBflen\fR must be less than RSA_size(\fBrsa\fR) \- 11 for the \s-1PKCS\s0 #1 v1.5 based padding modes, less than RSA_size(\fBrsa\fR) \- 41 for \&\s-1RSA_PKCS1_OAEP_PADDING\s0 and exactly RSA_size(\fBrsa\fR) for \s-1RSA_NO_PADDING.\s0 The random number generator must be seeded prior to calling \&\fBRSA_public_encrypt()\fR. .PP \&\fBRSA_private_decrypt()\fR decrypts the \fBflen\fR bytes at \fBfrom\fR using the private key \fBrsa\fR and stores the plaintext in \fBto\fR. \fBto\fR must point to a memory section large enough to hold the decrypted data (which is smaller than RSA_size(\fBrsa\fR)). \fBpadding\fR is the padding mode that was used to encrypt the data. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBRSA_public_encrypt()\fR returns the size of the encrypted data (i.e., RSA_size(\fBrsa\fR)). \fBRSA_private_decrypt()\fR returns the size of the recovered plaintext. .PP On error, \-1 is returned; the error codes can be obtained by \fBERR_get_error\fR\|(3). .SH "WARNING" .IX Header "WARNING" Decryption failures in the \s-1RSA_PKCS1_PADDING\s0 mode leak information which can potentially be used to mount a Bleichenbacher padding oracle attack. This is an inherent weakness in the \s-1PKCS\s0 #1 v1.5 padding design. Prefer \s-1RSA_PKCS1_OAEP_PADDING.\s0 .SH "CONFORMING TO" .IX Header "CONFORMING TO" \&\s-1SSL, PKCS\s0 #1 v2.0 .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBERR_get_error\fR\|(3), \fBrand\fR\|(3), \fBrsa\fR\|(3), \&\fBRSA_size\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" The \fBpadding\fR argument was added in SSLeay 0.8. \s-1RSA_NO_PADDING\s0 is available since SSLeay 0.9.0, \s-1OAEP\s0 was added in OpenSSL 0.9.2b.
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