D2I_RSAPUBLICKEY(3) | Library Functions Manual | D2I_RSAPUBLICKEY(3)

# NAME

`d2i_RSAPublicKey`, `i2d_RSAPublicKey`, `d2i_RSAPrivateKey`, `i2d_RSAPrivateKey`, `d2i_Netscape_RSA`, `i2d_Netscape_RSA`, `d2i_RSA_PSS_PARAMS`, `i2d_RSA_PSS_PARAMS`, `d2i_RSAPublicKey_bio`, `d2i_RSAPublicKey_fp`, `i2d_RSAPublicKey_bio`, `i2d_RSAPublicKey_fp`, `d2i_RSAPrivateKey_bio`, `d2i_RSAPrivateKey_fp`, `i2d_RSAPrivateKey_bio`, `i2d_RSAPrivateKey_fp`, `d2i_RSA_PUBKEY`, `i2d_RSA_PUBKEY`, `d2i_RSA_PUBKEY_bio`, `d2i_RSA_PUBKEY_fp`, `i2d_RSA_PUBKEY_bio`, `i2d_RSA_PUBKEY_fp` — decode and encode RSA keys and parameters

# SYNOPSIS

library “libcrypto”
`#include <openssl/rsa.h>`

RSA *
`d2i_RSAPublicKey`(RSA **val_out, const unsigned char **der_in, long length);

int
`i2d_RSAPublicKey`(RSA *val_in, unsigned char **der_out);

RSA *
`d2i_RSAPrivateKey`(RSA **val_out, const unsigned char **der_in, long length);

int
`i2d_RSAPrivateKey`(RSA *val_in, unsigned char **der_out);

RSA *
`d2i_Netscape_RSA`(RSA **val_out, const unsigned char **der_in, long length, int (*cb)());

int
`i2d_Netscape_RSA`(RSA *val_in, unsigned char **der_out, int (*cb)());

RSA_PSS_PARAMS *
`d2i_RSA_PSS_PARAMS`(RSA_PSS_PARAMS **val_out, const unsigned char **der_in, long length);

int
`i2d_RSA_PSS_PARAMS`(RSA_PSS_PARAMS *val_in, unsigned char **der_out);

`#include <openssl/x509.h>`

RSA *
`d2i_RSAPublicKey_bio`(BIO *in_bio, RSA **val_out);

RSA *
`d2i_RSAPublicKey_fp`(FILE *in_fp, RSA **val_out);

int
`i2d_RSAPublicKey_bio`(BIO *out_bio, RSA *val_in);

int
`i2d_RSAPublicKey_fp`(FILE *out_fp, RSA *val_in);

RSA *
`d2i_RSAPrivateKey_bio`(BIO *in_bio, RSA **val_out);

RSA *
`d2i_RSAPrivateKey_fp`(FILE *in_fp, RSA **val_out);

int
`i2d_RSAPrivateKey_bio`(BIO *out_bio, RSA *val_in);

int
`i2d_RSAPrivateKey_fp`(FILE *out_fp, RSA *val_in);

RSA *
`d2i_RSA_PUBKEY`(RSA **val_out, const unsigned char **der_in, long length);

int
`i2d_RSA_PUBKEY`(RSA *val_in, unsigned char **der_out);

RSA *
`d2i_RSA_PUBKEY_bio`(BIO *in_bio, RSA **val_out);

RSA *
`d2i_RSA_PUBKEY_fp`(FILE *in_fp, RSA **val_out);

int
`i2d_RSA_PUBKEY_bio`(BIO *out_bio, RSA *val_in);

int
`i2d_RSA_PUBKEY_fp`(FILE *out_fp, RSA *val_in);

# DESCRIPTION

These functions decode and encode RSA private and public keys. For details about the semantics, examples, caveats, and bugs, see ASN1_item_d2i(3).

`d2i_RSAPublicKey`() and `i2d_RSAPublicKey`() decode and encode a PKCS#1 RSAPublicKey structure defined in RFC 8017 appendix A.1.1. `d2i_RSAPublicKey_bio`(), `d2i_RSAPublicKey_fp`(), `i2d_RSAPublicKey_bio`(), and `i2d_RSAPublicKey_fp`() are similar except that they decode or encode using a BIO or FILE pointer.

`d2i_RSAPrivateKey`() and `i2d_RSAPrivateKey`() decode and encode a PKCS#1 RSAPrivateKey structure defined in RFC 8017 appendix A.1.2. The RSA structure passed to the private key encoding functions should have all the PKCS#1 private key components present. The data encoded by the private key functions is unencrypted and therefore offers no private key security. `d2i_RSAPrivateKey_bio`(), `d2i_RSAPrivateKey_fp`(), `i2d_RSAPrivateKey_bio`(), and `i2d_RSAPrivateKey_fp`() are similar except that they decode or encode using a BIO or FILE pointer.

`d2i_Netscape_RSA`() and `i2d_Netscape_RSA`() decode and encode an RSA private key in NET format. These functions are present to provide compatibility with certain very old software. The NET format has some severe security weaknesses and should be avoided if possible.

`d2i_RSA_PSS_PARAMS`() and `i2d_RSA_PSS_PARAMS`() decode and encode a PKCS#1 RSASSA-PSS-params structure defined in RFC 8017 appendix A.2.3 and documented in RSA_PSS_PARAMS_new(3).

`d2i_RSA_PUBKEY`() and `i2d_RSA_PUBKEY`() decode and encode an RSA public key using an ASN.1 SubjectPublicKeyInfo structure defined in RFC 5280 section 4.1 and documented in X509_PUBKEY_new(3). `d2i_RSA_PUBKEY_bio`(), `d2i_RSA_PUBKEY_fp`(), `i2d_RSA_PUBKEY_bio`(), and `i2d_RSA_PUBKEY_fp`() are similar except that they decode or encode using a BIO or FILE pointer.

# RETURN VALUES

`d2i_RSAPublicKey`(), `d2i_RSAPublicKey_bio`(), `d2i_RSAPublicKey_fp`(), `d2i_RSAPrivateKey`(), `d2i_RSAPrivateKey_bio`(), `d2i_RSAPrivateKey_fp`(), `d2i_Netscape_RSA`(), `d2i_RSA_PUBKEY`(), `d2i_RSA_PUBKEY_bio`(), and `d2i_RSA_PUBKEY_fp`() return a valid RSA object or `NULL` if an error occurs.

`d2i_RSA_PSS_PARAMS`() returns a valid RSA_PSS_PARAMS object or `NULL` if an error occurs.

`i2d_RSAPublicKey`(), `i2d_RSAPrivateKey`(), `i2d_Netscape_RSA`(), `i2d_RSA_PSS_PARAMS`(), and `i2d_RSA_PUBKEY`() return the number of bytes successfully encoded or a negative value if an error occurs.

`i2d_RSAPublicKey_bio`(), `i2d_RSAPublicKey_fp`(), `i2d_RSAPrivateKey_bio`(), `i2d_RSAPrivateKey_fp`(), `i2d_RSA_PUBKEY_bio`(), and `i2d_RSA_PUBKEY_fp`() return 1 for success or 0 if an error occurs.

# SEE ALSO

ASN1_item_d2i(3), EVP_PKEY_set1_RSA(3), PEM_write_RSAPrivateKey(3), RSA_new(3), RSA_PSS_PARAMS_new(3), X509_PUBKEY_new(3)

# STANDARDS

RFC 8017: PKCS #1: RSA Cryptography Specifications

RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile, section 4.1: Basic Certificate Fields

# HISTORY

`d2i_RSAPublicKey`(), `i2d_RSAPublicKey`(), `d2i_RSAPrivateKey`(), `i2d_RSAPrivateKey`(), `d2i_RSAPrivateKey_fp`(), `i2d_RSAPrivateKey_fp`(), `d2i_Netscape_RSA`(), and `i2d_Netscape_RSA`() first appeared in SSLeay 0.5.1. `d2i_RSAPrivateKey_bio`() and `i2d_RSAPrivateKey_bio`() first appeared in SSLeay 0.6.0. `d2i_RSAPublicKey_bio`(), `d2i_RSAPublicKey_fp`(), `i2d_RSAPublicKey_bio`(), and `i2d_RSAPublicKey_fp`() first appeared in SSLeay 0.8.1. These functions have been available since OpenBSD 2.4.

`d2i_RSA_PUBKEY`(), `i2d_RSA_PUBKEY`(), `d2i_RSA_PUBKEY_bio`(), `d2i_RSA_PUBKEY_fp`(), `i2d_RSA_PUBKEY_bio`(), and `i2d_RSA_PUBKEY_fp`() first appeared in OpenSSL 0.9.5 and have been available since OpenBSD 2.7.

`d2i_RSA_PSS_PARAMS`() and `i2d_RSA_PSS_PARAMS`() first appeared in OpenSSL 1.0.1 and have been available since OpenBSD 5.3.

June 8, 2025 | Debian