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RSA_public_encrypt(3) OpenSSL RSA_public_encrypt(3)NAMERSA_public_encrypt, RSA_private_decrypt - RSA public key cryptographyLIBRARYlibcrypto, -lcryptoSYNOPSIS#include <openssl/rsa.h> int RSA_public_encrypt(int flen, unsigned char *from, unsigned char *to, RSA *rsa, int padding); int RSA_private_decrypt(int flen, unsigned char *from, unsigned char *to, RSA *rsa, int padding);DESCRIPTIONRSA_public_encrypt() encrypts theflenbytes atfrom(usually a session key) using the public keyrsaand stores the ciphertext into.tomust point to RSA_size(rsa) bytes of memory.paddingdenotes 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 applications. 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 only be used to implement cryptographically sound padding modes in the application code. Encrypting user data directly with RSA is insecure.flenmust be less than RSA_size(rsa) - 11 for the PKCS #1 v1.5 based padding modes, less than RSA_size(rsa) - 41 for RSA_PKCS1_OAEP_PADDING and exactly RSA_size(rsa) for RSA_NO_PADDING. The random number generator must be seeded prior to calling RSA_public_encrypt(). RSA_private_decrypt() decrypts theflenbytes atfromusing the private keyrsaand stores the plaintext into.tomust point to a memory section large enough to hold the decrypted data (which is smaller than RSA_size(rsa)).paddingis the padding mode that was used to encrypt the data.RETURNVALUESRSA_public_encrypt() returns the size of the encrypted data (i.e., RSA_size(rsa)). RSA_private_decrypt() returns the size of the recovered plaintext. On error, -1 is returned; the error codes can be obtained by ERR_get_error(3).CONFORMINGTOSSL, PKCS #1 v2.0SEEALSOERR_get_error(3), openssl_rand(3), openssl_rsa(3), RSA_size(3)HISTORYThepaddingargument was added in SSLeay 0.8. RSA_NO_PADDING is available since SSLeay 0.9.0, OAEP was added in OpenSSL 0.9.2b. 1.0.2k 2009-07-19 RSA_public_encrypt(3)