RSA_public_encrypt(3) OpenSSL RSA_public_encrypt(3) NNAAMMEE RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography SSYYNNOOPPSSIISS #include 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); DDEESSCCRRIIPPTTIIOONN _R_S_A___p_u_b_l_i_c___e_n_c_r_y_p_t_(_) encrypts the fflleenn bytes at ffrroomm (usually a session key) using the public key rrssaa and stores the ciphertext in ttoo. ttoo must point to RSA_size(rrssaa) bytes of memory. ppaaddddiinngg denotes one of the following modes: RSA_PKCS1_PADDING PKCS #1 v1.5 padding. This currently is the most widely used mode. RSA_PKCS1_OAEP_PADDING EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty encoding parameter. This mode is recommended for all new applica- tions. RSA_SSLV23_PADDING PKCS #1 v1.5 padding with an SSL-specific modification that denotes that the server is SSL3 capable. RSA_NO_PADDING Raw RSA encryption. This mode should _o_n_l_y be used to implement cryptographically sound padding modes in the application code. Encrypting user data directly with RSA is insecure. fflleenn must be less than RSA_size(rrssaa) - 11 for the PKCS #1 v1.5 based padding modes, less than RSA_size(rrssaa) - 41 for RSA_PKCS1_OAEP_PADDING and exactly RSA_size(rrssaa) for RSA_NO_PADDING. The random number gener- ator must be seeded prior to calling _R_S_A___p_u_b_l_i_c___e_n_c_r_y_p_t_(_). _R_S_A___p_r_i_v_a_t_e___d_e_c_r_y_p_t_(_) decrypts the fflleenn bytes at ffrroomm using the private key rrssaa and stores the plaintext in ttoo. ttoo must point to a memory sec- tion large enough to hold the decrypted data (which is smaller than RSA_size(rrssaa)). ppaaddddiinngg is the padding mode that was used to encrypt the data. RREETTUURRNN VVAALLUUEESS _R_S_A___p_u_b_l_i_c___e_n_c_r_y_p_t_(_) returns the size of the encrypted data (i.e., RSA_size(rrssaa)). _R_S_A___p_r_i_v_a_t_e___d_e_c_r_y_p_t_(_) returns the size of the recovered plaintext. On error, -1 is returned; the error codes can be obtained by _E_R_R___g_e_t___e_r_r_o_r(3). WWAARRNNIINNGG Decryption failures in the RSA_PKCS1_PADDING mode leak information which can potentially be used to mount a Bleichenbacher padding oracle attack. This is an inherent weakness in the PKCS #1 v1.5 padding design. Prefer RSA_PKCS1_OAEP_PADDING. CCOONNFFOORRMMIINNGG TTOO SSL, PKCS #1 v2.0 SSEEEE AALLSSOO _E_R_R___g_e_t___e_r_r_o_r(3), _r_a_n_d(3), _r_s_a(3), _R_S_A___s_i_z_e(3) HHIISSTTOORRYY The ppaaddddiinngg argument was added in SSLeay 0.8. RSA_NO_PADDING is avail- able since SSLeay 0.9.0, OAEP was added in OpenSSL 0.9.2b. 1.0.2u 2019-12-20 RSA_public_encrypt(3)