1RSA_PUBLIC_ENCRYPT(3ossl) OpenSSL RSA_PUBLIC_ENCRYPT(3ossl)
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6 RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography
7
9 #include <openssl/rsa.h>
10 The following functions have been deprecated since OpenSSL 3.0, and can
12 be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
13 version value, see openssl_user_macros(7):
14 int RSA_public_encrypt(int flen, const unsigned char *from,
16 unsigned char *to, RSA *rsa, int padding);
17 int RSA_private_decrypt(int flen, const unsigned char *from,
19 unsigned char *to, RSA *rsa, int padding);
20
22 Both of the functions described on this page are deprecated.
23 Applications should instead use EVP_PKEY_encrypt_init_ex(3),
24 EVP_PKEY_encrypt(3), EVP_PKEY_decrypt_init_ex(3) and
25 EVP_PKEY_decrypt(3).
26 RSA_public_encrypt() encrypts the flen bytes at from (usually a session
28 key) using the public key rsa and stores the ciphertext in to. to must
29 point to RSA_size(rsa) bytes of memory.
30 padding denotes one of the following modes:
32 RSA_PKCS1_PADDING
34 PKCS #1 v1.5 padding. This currently is the most widely used mode.
35 However, it is highly recommended to use RSA_PKCS1_OAEP_PADDING in
36 new applications. SEE WARNING BELOW.
37 RSA_PKCS1_OAEP_PADDING
39 EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty
40 encoding parameter. This mode is recommended for all new
41 applications.
42 RSA_NO_PADDING
44 Raw RSA encryption. This mode should only be used to implement
45 cryptographically sound padding modes in the application code.
46 Encrypting user data directly with RSA is insecure.
47 flen must not be more than RSA_size(rsa) - 11 for the PKCS #1 v1.5
49 based padding modes, not more than RSA_size(rsa) - 42 for
50 RSA_PKCS1_OAEP_PADDING and exactly RSA_size(rsa) for RSA_NO_PADDING.
51 When a padding mode other than RSA_NO_PADDING is in use, then
52 RSA_public_encrypt() will include some random bytes into the ciphertext
53 and therefore the ciphertext will be different each time, even if the
54 plaintext and the public key are exactly identical. The returned
55 ciphertext in to will always be zero padded to exactly RSA_size(rsa)
56 bytes. to and from may overlap.
57 RSA_private_decrypt() decrypts the flen bytes at from using the private
59 key rsa and stores the plaintext in to. flen should be equal to
60 RSA_size(rsa) but may be smaller, when leading zero bytes are in the
61 ciphertext. Those are not important and may be removed, but
62 RSA_public_encrypt() does not do that. to must point to a memory
63 section large enough to hold the maximal possible decrypted data (which
64 is equal to RSA_size(rsa) for RSA_NO_PADDING, RSA_size(rsa) - 11 for
65 the PKCS #1 v1.5 based padding modes and RSA_size(rsa) - 42 for
66 RSA_PKCS1_OAEP_PADDING). padding is the padding mode that was used to
67 encrypt the data. to and from may overlap.
68
70 RSA_public_encrypt() returns the size of the encrypted data (i.e.,
71 RSA_size(rsa)). RSA_private_decrypt() returns the size of the recovered
72 plaintext. A return value of 0 is not an error and means only that the
73 plaintext was empty.
74 On error, -1 is returned; the error codes can be obtained by
76 ERR_get_error(3).
77
79 Decryption failures in the RSA_PKCS1_PADDING mode leak information
80 which can potentially be used to mount a Bleichenbacher padding oracle
81 attack. This is an inherent weakness in the PKCS #1 v1.5 padding
82 design. Prefer RSA_PKCS1_OAEP_PADDING.
83
85 SSL, PKCS #1 v2.0
86
88 ERR_get_error(3), RAND_bytes(3), RSA_size(3)
89
91 Both of these functions were deprecated in OpenSSL 3.0.
92
94 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
95 Licensed under the Apache License 2.0 (the "License"). You may not use
97 this file except in compliance with the License. You can obtain a copy
98 in the file LICENSE in the source distribution or at
99 <https://www.openssl.org/source/license.html>.
1003.0.5 2022-11-01 RSA_PUBLIC_ENCRYPT(3ossl)