1 .\" $OpenBSD: RSA_public_encrypt.3,v 1.11 2018/03/27 17:35:50 schwarze Exp $
2 .\" OpenSSL RSA_public_encrypt.pod 1e3f62a3 Jul 17 16:47:13 2017 +0200
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51 .Dd $Mdocdate: March 27 2018 $
52 .Dt RSA_PUBLIC_ENCRYPT 3
55 .Nm RSA_public_encrypt ,
56 .Nm RSA_private_decrypt
57 .Nd RSA public key cryptography
61 .Fo RSA_public_encrypt
63 .Fa "const unsigned char *from"
64 .Fa "unsigned char *to"
69 .Fo RSA_private_decrypt
71 .Fa "const unsigned char *from"
72 .Fa "unsigned char *to"
77 .Fn RSA_public_encrypt
82 (usually a session key) using the public key
84 and stores the ciphertext in
92 denotes one of the following modes:
94 .It Dv RSA_PKCS1_PADDING
96 This currently is the most widely used mode.
97 .It Dv RSA_PKCS1_OAEP_PADDING
98 EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty
100 This mode is recommended for all new applications.
101 .It Dv RSA_NO_PADDING
103 This mode should only be used to implement cryptographically sound
104 padding modes in the application code.
105 Encrypting user data directly with RSA is insecure.
111 - 11 for the PKCS #1 v1.5 based padding modes, less than
114 .Dv RSA_PKCS1_OAEP_PADDING
120 .Fn RSA_private_decrypt
125 using the private key
127 and stores the plaintext in
130 must point to a memory section large enough to hold the decrypted data
131 (which is smaller than
134 is the padding mode that was used to encrypt the data.
136 .Fn RSA_public_encrypt
137 returns the size of the encrypted data (i.e.\&
139 .Fn RSA_private_decrypt
140 returns the size of the recovered plaintext.
142 On error, -1 is returned; the error codes can be obtained by
143 .Xr ERR_get_error 3 .
145 .Xr ERR_get_error 3 ,
146 .Xr RSA_meth_set_priv_dec 3 ,
152 .Fn RSA_public_encrypt
154 .Fn RSA_private_decrypt
155 appeared in SSLeay 0.4 or earlier and have been available since
159 is available since SSLeay 0.9.0.
160 OAEP was added in OpenSSL 0.9.2b.
162 Decryption failures in the
163 .Dv RSA_PKCS1_PADDING
164 mode leak information which can potentially be used to mount a
165 Bleichenbacher padding oracle attack.
166 This is an inherent weakness in the PKCS #1 v1.5 padding design.
168 .Dv RSA_PKCS1_OAEP_PADDING .