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RSA_NEW(3) Library Functions Manual RSA_NEW(3)

RSA_new, RSA_up_ref, RSA_free
allocate and free RSA objects

#include <openssl/rsa.h>
RSA_up_ref(RSA *rsa);
RSA_free(RSA *rsa);

The RSA functions implement RSA public key encryption and signatures as defined in PKCS #1 v2.0 (RFC 2437).
RSA_new() allocates and initializes an RSA structure, setting the reference count to 1. It is equivalent to calling RSA_new_method(3) with a NULL argument.
RSA_up_ref() increments the reference count by 1.
RSA_free() decrements the reference count by 1. If it reaches 0, it frees the RSA structure and its components. The key is erased before the memory is returned to the system. If rsa is a NULL pointer, no action occurs.
The RSA structure consists of several BIGNUM components. It can contain public as well as private RSA keys:
typedef struct { 
	BIGNUM *n;		// public modulus 
	BIGNUM *e;		// public exponent 
	BIGNUM *d;		// private exponent 
	BIGNUM *p;		// secret prime factor 
	BIGNUM *q;		// secret prime factor 
	BIGNUM *dmp1;		// d mod (p-1) 
	BIGNUM *dmq1;		// d mod (q-1) 
	BIGNUM *iqmp;		// q^-1 mod p 
	// ... 
} RSA;
In public keys, the private exponent d and the related secret values p, q, dmp1, dmp2, and iqmp are NULL.
p, q, dmp1, dmq1, and iqmp may be NULL in private keys, but the RSA operations are much faster when these values are available.
Note that RSA keys may use non-standard RSA_METHOD implementations, either directly or by the use of ENGINE modules. In some cases (e.g. an ENGINE providing support for hardware-embedded keys), these BIGNUM values will not be used by the implementation or may be used for alternative data storage. For this reason, applications should generally avoid using RSA structure elements directly and instead use API functions to query or modify keys.

If the allocation fails, RSA_new() returns NULL and sets an error code that can be obtained by ERR_get_error(3). Otherwise it returns a pointer to the newly allocated structure.
RSA_up_ref() returns 1 for success or 0 for failure.

BN_new(3), d2i_RSAPublicKey(3), DH_new(3), DSA_new(3), ERR_get_error(3), EVP_PKEY_set1_RSA(3), RSA_blinding_on(3), RSA_check_key(3), RSA_generate_key(3), RSA_get0_key(3), RSA_get_ex_new_index(3), RSA_meth_new(3), RSA_padding_add_PKCS1_type_1(3), RSA_print(3), RSA_private_encrypt(3), RSA_public_encrypt(3), RSA_set_method(3), RSA_sign(3), RSA_sign_ASN1_OCTET_STRING(3), RSA_size(3)

SSL, PKCS #1 v2.0
RSA was covered by a US patent which expired in September 2000.

RSA_new() and RSA_free() appeared in SSLeay 0.4 or earlier and have been available since OpenBSD 2.4.
RSA_up_ref() first appeared in OpenSSL 0.9.7 and has been available since OpenBSD 3.2.
April 18, 2018 OpenBSD-current