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Title "EVP_PKEY_CTX_CTRL 3ossl"
EVP_PKEY_CTX_CTRL 3ossl "2023-09-19" "3.0.11" "OpenSSL"
For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
"NAME"
EVP_PKEY_CTX_ctrl, EVP_PKEY_CTX_ctrl_str, EVP_PKEY_CTX_ctrl_uint64, EVP_PKEY_CTX_md, EVP_PKEY_CTX_set_signature_md, EVP_PKEY_CTX_get_signature_md, EVP_PKEY_CTX_set_mac_key, EVP_PKEY_CTX_set_group_name, EVP_PKEY_CTX_get_group_name, EVP_PKEY_CTX_set_rsa_padding, EVP_PKEY_CTX_get_rsa_padding, EVP_PKEY_CTX_set_rsa_pss_saltlen, EVP_PKEY_CTX_get_rsa_pss_saltlen, EVP_PKEY_CTX_set_rsa_keygen_bits, EVP_PKEY_CTX_set_rsa_keygen_pubexp, EVP_PKEY_CTX_set1_rsa_keygen_pubexp, EVP_PKEY_CTX_set_rsa_keygen_primes, EVP_PKEY_CTX_set_rsa_mgf1_md_name, EVP_PKEY_CTX_set_rsa_mgf1_md, EVP_PKEY_CTX_get_rsa_mgf1_md, EVP_PKEY_CTX_get_rsa_mgf1_md_name, EVP_PKEY_CTX_set_rsa_oaep_md_name, EVP_PKEY_CTX_set_rsa_oaep_md, EVP_PKEY_CTX_get_rsa_oaep_md, EVP_PKEY_CTX_get_rsa_oaep_md_name, EVP_PKEY_CTX_set0_rsa_oaep_label, EVP_PKEY_CTX_get0_rsa_oaep_label, EVP_PKEY_CTX_set_dsa_paramgen_bits, EVP_PKEY_CTX_set_dsa_paramgen_q_bits, EVP_PKEY_CTX_set_dsa_paramgen_md, EVP_PKEY_CTX_set_dsa_paramgen_md_props, EVP_PKEY_CTX_set_dsa_paramgen_gindex, EVP_PKEY_CTX_set_dsa_paramgen_type, EVP_PKEY_CTX_set_dsa_paramgen_seed, EVP_PKEY_CTX_set_dh_paramgen_prime_len, EVP_PKEY_CTX_set_dh_paramgen_subprime_len, EVP_PKEY_CTX_set_dh_paramgen_generator, EVP_PKEY_CTX_set_dh_paramgen_type, EVP_PKEY_CTX_set_dh_paramgen_gindex, EVP_PKEY_CTX_set_dh_paramgen_seed, EVP_PKEY_CTX_set_dh_rfc5114, EVP_PKEY_CTX_set_dhx_rfc5114, EVP_PKEY_CTX_set_dh_pad, EVP_PKEY_CTX_set_dh_nid, EVP_PKEY_CTX_set_dh_kdf_type, EVP_PKEY_CTX_get_dh_kdf_type, EVP_PKEY_CTX_set0_dh_kdf_oid, EVP_PKEY_CTX_get0_dh_kdf_oid, EVP_PKEY_CTX_set_dh_kdf_md, EVP_PKEY_CTX_get_dh_kdf_md, EVP_PKEY_CTX_set_dh_kdf_outlen, EVP_PKEY_CTX_get_dh_kdf_outlen, EVP_PKEY_CTX_set0_dh_kdf_ukm, EVP_PKEY_CTX_get0_dh_kdf_ukm, EVP_PKEY_CTX_set_ec_paramgen_curve_nid, EVP_PKEY_CTX_set_ec_param_enc, EVP_PKEY_CTX_set_ecdh_cofactor_mode, EVP_PKEY_CTX_get_ecdh_cofactor_mode, EVP_PKEY_CTX_set_ecdh_kdf_type, EVP_PKEY_CTX_get_ecdh_kdf_type, EVP_PKEY_CTX_set_ecdh_kdf_md, EVP_PKEY_CTX_get_ecdh_kdf_md, EVP_PKEY_CTX_set_ecdh_kdf_outlen, EVP_PKEY_CTX_get_ecdh_kdf_outlen, EVP_PKEY_CTX_set0_ecdh_kdf_ukm, EVP_PKEY_CTX_get0_ecdh_kdf_ukm, EVP_PKEY_CTX_set1_id, EVP_PKEY_CTX_get1_id, EVP_PKEY_CTX_get1_id_len, EVP_PKEY_CTX_set_kem_op \- algorithm specific control operations
"SYNOPSIS"
Header "SYNOPSIS" .Vb 1 #include <openssl/evp.h> \& int EVP_PKEY_CTX_ctrl(EVP_PKEY_CTX *ctx, int keytype, int optype, int cmd, int p1, void *p2); int EVP_PKEY_CTX_ctrl_uint64(EVP_PKEY_CTX *ctx, int keytype, int optype, int cmd, uint64_t value); int EVP_PKEY_CTX_ctrl_str(EVP_PKEY_CTX *ctx, const char *type, const char *value); \& int EVP_PKEY_CTX_md(EVP_PKEY_CTX *ctx, int optype, int cmd, const char *md); \& int EVP_PKEY_CTX_set_signature_md(EVP_PKEY_CTX *ctx, const EVP_MD *md); int EVP_PKEY_CTX_get_signature_md(EVP_PKEY_CTX *ctx, const EVP_MD **pmd); \& int EVP_PKEY_CTX_set_mac_key(EVP_PKEY_CTX *ctx, const unsigned char *key, int len); int EVP_PKEY_CTX_set_group_name(EVP_PKEY_CTX *ctx, const char *name); int EVP_PKEY_CTX_get_group_name(EVP_PKEY_CTX *ctx, char *name, size_t namelen); \& int EVP_PKEY_CTX_set_kem_op(EVP_PKEY_CTX *ctx, const char *op); \& #include <openssl/rsa.h> \& int EVP_PKEY_CTX_set_rsa_padding(EVP_PKEY_CTX *ctx, int pad); int EVP_PKEY_CTX_get_rsa_padding(EVP_PKEY_CTX *ctx, int *pad); int EVP_PKEY_CTX_set_rsa_pss_saltlen(EVP_PKEY_CTX *ctx, int saltlen); int EVP_PKEY_CTX_get_rsa_pss_saltlen(EVP_PKEY_CTX *ctx, int *saltlen); int EVP_PKEY_CTX_set_rsa_keygen_bits(EVP_PKEY_CTX *ctx, int mbits); int EVP_PKEY_CTX_set1_rsa_keygen_pubexp(EVP_PKEY_CTX *ctx, BIGNUM *pubexp); int EVP_PKEY_CTX_set_rsa_keygen_primes(EVP_PKEY_CTX *ctx, int primes); int EVP_PKEY_CTX_set_rsa_mgf1_md_name(EVP_PKEY_CTX *ctx, const char *mdname, const char *mdprops); int EVP_PKEY_CTX_set_rsa_mgf1_md(EVP_PKEY_CTX *ctx, const EVP_MD *md); int EVP_PKEY_CTX_get_rsa_mgf1_md(EVP_PKEY_CTX *ctx, const EVP_MD **md); int EVP_PKEY_CTX_get_rsa_mgf1_md_name(EVP_PKEY_CTX *ctx, char *name, size_t namelen); int EVP_PKEY_CTX_set_rsa_oaep_md_name(EVP_PKEY_CTX *ctx, const char *mdname, const char *mdprops); int EVP_PKEY_CTX_set_rsa_oaep_md(EVP_PKEY_CTX *ctx, const EVP_MD *md); int EVP_PKEY_CTX_get_rsa_oaep_md(EVP_PKEY_CTX *ctx, const EVP_MD **md); int EVP_PKEY_CTX_get_rsa_oaep_md_name(EVP_PKEY_CTX *ctx, char *name, size_t namelen); int EVP_PKEY_CTX_set0_rsa_oaep_label(EVP_PKEY_CTX *ctx, void *label, int len); int EVP_PKEY_CTX_get0_rsa_oaep_label(EVP_PKEY_CTX *ctx, unsigned char **label); \& #include <openssl/dsa.h> \& int EVP_PKEY_CTX_set_dsa_paramgen_bits(EVP_PKEY_CTX *ctx, int nbits); int EVP_PKEY_CTX_set_dsa_paramgen_q_bits(EVP_PKEY_CTX *ctx, int qbits); int EVP_PKEY_CTX_set_dsa_paramgen_md(EVP_PKEY_CTX *ctx, const EVP_MD *md); int EVP_PKEY_CTX_set_dsa_paramgen_md_props(EVP_PKEY_CTX *ctx, const char *md_name, const char *md_properties); int EVP_PKEY_CTX_set_dsa_paramgen_type(EVP_PKEY_CTX *ctx, const char *name); int EVP_PKEY_CTX_set_dsa_paramgen_gindex(EVP_PKEY_CTX *ctx, int gindex); int EVP_PKEY_CTX_set_dsa_paramgen_seed(EVP_PKEY_CTX *ctx, const unsigned char *seed, size_t seedlen); \& #include <openssl/dh.h> \& int EVP_PKEY_CTX_set_dh_paramgen_prime_len(EVP_PKEY_CTX *ctx, int len); int EVP_PKEY_CTX_set_dh_paramgen_subprime_len(EVP_PKEY_CTX *ctx, int len); int EVP_PKEY_CTX_set_dh_paramgen_generator(EVP_PKEY_CTX *ctx, int gen); int EVP_PKEY_CTX_set_dh_paramgen_type(EVP_PKEY_CTX *ctx, int type); int EVP_PKEY_CTX_set_dh_pad(EVP_PKEY_CTX *ctx, int pad); int EVP_PKEY_CTX_set_dh_nid(EVP_PKEY_CTX *ctx, int nid); int EVP_PKEY_CTX_set_dh_rfc5114(EVP_PKEY_CTX *ctx, int rfc5114); int EVP_PKEY_CTX_set_dhx_rfc5114(EVP_PKEY_CTX *ctx, int rfc5114); int EVP_PKEY_CTX_set_dh_paramgen_gindex(EVP_PKEY_CTX *ctx, int gindex); int EVP_PKEY_CTX_set_dh_paramgen_seed(EVP_PKEY_CTX *ctx, const unsigned char *seed, size_t seedlen); int EVP_PKEY_CTX_set_dh_kdf_type(EVP_PKEY_CTX *ctx, int kdf); int EVP_PKEY_CTX_get_dh_kdf_type(EVP_PKEY_CTX *ctx); int EVP_PKEY_CTX_set0_dh_kdf_oid(EVP_PKEY_CTX *ctx, ASN1_OBJECT *oid); int EVP_PKEY_CTX_get0_dh_kdf_oid(EVP_PKEY_CTX *ctx, ASN1_OBJECT **oid); int EVP_PKEY_CTX_set_dh_kdf_md(EVP_PKEY_CTX *ctx, const EVP_MD *md); int EVP_PKEY_CTX_get_dh_kdf_md(EVP_PKEY_CTX *ctx, const EVP_MD **md); int EVP_PKEY_CTX_set_dh_kdf_outlen(EVP_PKEY_CTX *ctx, int len); int EVP_PKEY_CTX_get_dh_kdf_outlen(EVP_PKEY_CTX *ctx, int *len); int EVP_PKEY_CTX_set0_dh_kdf_ukm(EVP_PKEY_CTX *ctx, unsigned char *ukm, int len); \& #include <openssl/ec.h> \& int EVP_PKEY_CTX_set_ec_paramgen_curve_nid(EVP_PKEY_CTX *ctx, int nid); int EVP_PKEY_CTX_set_ec_param_enc(EVP_PKEY_CTX *ctx, int param_enc); int EVP_PKEY_CTX_set_ecdh_cofactor_mode(EVP_PKEY_CTX *ctx, int cofactor_mode); int EVP_PKEY_CTX_get_ecdh_cofactor_mode(EVP_PKEY_CTX *ctx); int EVP_PKEY_CTX_set_ecdh_kdf_type(EVP_PKEY_CTX *ctx, int kdf); int EVP_PKEY_CTX_get_ecdh_kdf_type(EVP_PKEY_CTX *ctx); int EVP_PKEY_CTX_set_ecdh_kdf_md(EVP_PKEY_CTX *ctx, const EVP_MD *md); int EVP_PKEY_CTX_get_ecdh_kdf_md(EVP_PKEY_CTX *ctx, const EVP_MD **md); int EVP_PKEY_CTX_set_ecdh_kdf_outlen(EVP_PKEY_CTX *ctx, int len); int EVP_PKEY_CTX_get_ecdh_kdf_outlen(EVP_PKEY_CTX *ctx, int *len); int EVP_PKEY_CTX_set0_ecdh_kdf_ukm(EVP_PKEY_CTX *ctx, unsigned char *ukm, int len); \& int EVP_PKEY_CTX_set1_id(EVP_PKEY_CTX *ctx, void *id, size_t id_len); int EVP_PKEY_CTX_get1_id(EVP_PKEY_CTX *ctx, void *id); int EVP_PKEY_CTX_get1_id_len(EVP_PKEY_CTX *ctx, size_t *id_len); .Ve

The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely by defining \s-1OPENSSL_API_COMPAT\s0 with a suitable version value, see openssl_user_macros\|(7):

.Vb 1 #include <openssl/rsa.h> \& int EVP_PKEY_CTX_set_rsa_keygen_pubexp(EVP_PKEY_CTX *ctx, BIGNUM *pubexp); \& #include <openssl/dh.h> \& int EVP_PKEY_CTX_get0_dh_kdf_ukm(EVP_PKEY_CTX *ctx, unsigned char **ukm); \& #include <openssl/ec.h> \& int EVP_PKEY_CTX_get0_ecdh_kdf_ukm(EVP_PKEY_CTX *ctx, unsigned char **ukm); .Ve

"DESCRIPTION"
Header "DESCRIPTION" \fBEVP_PKEY_CTX_ctrl() sends a control operation to the context ctx. The key type used must match keytype if it is not -1. The parameter optype is a mask indicating which operations the control can be applied to. The control command is indicated in cmd and any additional arguments in \fIp1 and p2.

For cmd = \s-1EVP_PKEY_CTRL_SET_MAC_KEY\s0, p1 is the length of the \s-1MAC\s0 key, and p2 is the \s-1MAC\s0 key. This is used by Poly1305, SipHash, \s-1HMAC\s0 and \s-1CMAC.\s0

Applications will not normally call EVP_PKEY_CTX_ctrl() directly but will instead call one of the algorithm specific functions below.

\fBEVP_PKEY_CTX_ctrl_uint64() is a wrapper that directly passes a uint64 value as p2 to EVP_PKEY_CTX_ctrl().

\fBEVP_PKEY_CTX_ctrl_str() allows an application to send an algorithm specific control operation to a context ctx in string form. This is intended to be used for options specified on the command line or in text files. The commands supported are documented in the openssl utility command line pages for the option -pkeyopt which is supported by the \fIpkeyutl, genpkey and req commands.

\fBEVP_PKEY_CTX_md() sends a message digest control operation to the context \fIctx. The message digest is specified by its name md.

\fBEVP_PKEY_CTX_set_signature_md() sets the message digest type used in a signature. It can be used in the \s-1RSA, DSA\s0 and \s-1ECDSA\s0 algorithms.

\fBEVP_PKEY_CTX_get_signature_md()gets the message digest type used in a signature. It can be used in the \s-1RSA, DSA\s0 and \s-1ECDSA\s0 algorithms.

Key generation typically involves setting up parameters to be used and generating the private and public key data. Some algorithm implementations allow private key data to be set explicitly using EVP_PKEY_CTX_set_mac_key(). In this case key generation is simply the process of setting up the parameters for the key and then setting the raw key data to the value explicitly. Normally applications would call EVP_PKEY_new_raw_private_key\|(3) or similar functions instead.

\fBEVP_PKEY_CTX_set_mac_key() can be used with any of the algorithms supported by the EVP_PKEY_new_raw_private_key\|(3) function.

\fBEVP_PKEY_CTX_set_group_name() sets the group name to name for parameter and key generation. For example for \s-1EC\s0 keys this will set the curve name and for \s-1DH\s0 keys it will set the name of the finite field group.

\fBEVP_PKEY_CTX_get_group_name() finds the group name that's currently set with ctx, and writes it to the location that name points at, as long as its size namelen is large enough to store that name, including a terminating \s-1NUL\s0 byte.

"\s-1RSA\s0 parameters"
Subsection "RSA parameters" \fBEVP_PKEY_CTX_set_rsa_padding() sets the \s-1RSA\s0 padding mode for ctx. The pad parameter can take the value \s-1RSA_PKCS1_PADDING\s0 for PKCS#1 padding, \s-1RSA_NO_PADDING\s0 for no padding, \s-1RSA_PKCS1_OAEP_PADDING\s0 for \s-1OAEP\s0 padding (encrypt and decrypt only), \s-1RSA_X931_PADDING\s0 for X9.31 padding (signature operations only), \s-1RSA_PKCS1_PSS_PADDING\s0 (sign and verify only) and \fB\s-1RSA_PKCS1_WITH_TLS_PADDING\s0 for \s-1TLS RSA\s0 ClientKeyExchange message padding (decryption only).

Two \s-1RSA\s0 padding modes behave differently if EVP_PKEY_CTX_set_signature_md() is used. If this function is called for PKCS#1 padding the plaintext buffer is an actual digest value and is encapsulated in a DigestInfo structure according to PKCS#1 when signing and this structure is expected (and stripped off) when verifying. If this control is not used with \s-1RSA\s0 and PKCS#1 padding then the supplied data is used directly and not encapsulated. In the case of X9.31 padding for \s-1RSA\s0 the algorithm identifier byte is added or checked and removed if this control is called. If it is not called then the first byte of the plaintext buffer is expected to be the algorithm identifier byte.

\fBEVP_PKEY_CTX_get_rsa_padding() gets the \s-1RSA\s0 padding mode for ctx.

\fBEVP_PKEY_CTX_set_rsa_pss_saltlen() sets the \s-1RSA PSS\s0 salt length to saltlen. As its name implies it is only supported for \s-1PSS\s0 padding. If this function is not called then the maximum salt length is used when signing and auto detection when verifying. Three special values are supported:

"\s-1RSA_PSS_SALTLEN_DIGEST\s0" 4
Item "RSA_PSS_SALTLEN_DIGEST" sets the salt length to the digest length.
"\s-1RSA_PSS_SALTLEN_MAX\s0" 4
Item "RSA_PSS_SALTLEN_MAX" sets the salt length to the maximum permissible value.
"\s-1RSA_PSS_SALTLEN_AUTO\s0" 4
Item "RSA_PSS_SALTLEN_AUTO" causes the salt length to be automatically determined based on the \fB\s-1PSS\s0 block structure when verifying. When signing, it has the same meaning as \s-1RSA_PSS_SALTLEN_MAX\s0.

\fBEVP_PKEY_CTX_get_rsa_pss_saltlen() gets the \s-1RSA PSS\s0 salt length for ctx. The padding mode must already have been set to \s-1RSA_PKCS1_PSS_PADDING\s0.

\fBEVP_PKEY_CTX_set_rsa_keygen_bits() sets the \s-1RSA\s0 key length for \s-1RSA\s0 key generation to bits. If not specified 2048 bits is used.

\fBEVP_PKEY_CTX_set1_rsa_keygen_pubexp() sets the public exponent value for \s-1RSA\s0 key generation to the value stored in pubexp. Currently it should be an odd integer. In accordance with the OpenSSL naming convention, the pubexp pointer must be freed independently of the \s-1EVP_PKEY_CTX\s0 (ie, it is internally copied). If not specified 65537 is used.

\fBEVP_PKEY_CTX_set_rsa_keygen_pubexp() does the same as \fBEVP_PKEY_CTX_set1_rsa_keygen_pubexp() except that there is no internal copy and therefore pubexp should not be modified or freed after the call.

\fBEVP_PKEY_CTX_set_rsa_keygen_primes() sets the number of primes for \s-1RSA\s0 key generation to primes. If not specified 2 is used.

\fBEVP_PKEY_CTX_set_rsa_mgf1_md_name() sets the \s-1MGF1\s0 digest for \s-1RSA\s0 padding schemes to the digest named mdname. If the \s-1RSA\s0 algorithm implementation for the selected provider supports it then the digest will be fetched using the properties mdprops. If not explicitly set the signing digest is used. The padding mode must have been set to \s-1RSA_PKCS1_OAEP_PADDING\s0 or \s-1RSA_PKCS1_PSS_PADDING\s0.

\fBEVP_PKEY_CTX_set_rsa_mgf1_md() does the same as \fBEVP_PKEY_CTX_set_rsa_mgf1_md_name() except that the name of the digest is inferred from the supplied md and it is not possible to specify any properties.

\fBEVP_PKEY_CTX_get_rsa_mgf1_md_name() gets the name of the \s-1MGF1\s0 digest algorithm for ctx. If not explicitly set the signing digest is used. The padding mode must have been set to \s-1RSA_PKCS1_OAEP_PADDING\s0 or \fB\s-1RSA_PKCS1_PSS_PADDING\s0.

\fBEVP_PKEY_CTX_get_rsa_mgf1_md() does the same as \fBEVP_PKEY_CTX_get_rsa_mgf1_md_name() except that it returns a pointer to an \s-1EVP_MD\s0 object instead. Note that only known, built-in \s-1EVP_MD\s0 objects will be returned. The \s-1EVP_MD\s0 object may be \s-1NULL\s0 if the digest is not one of these (such as a digest only implemented in a third party provider).

\fBEVP_PKEY_CTX_set_rsa_oaep_md_name() sets the message digest type used in \s-1RSA OAEP\s0 to the digest named mdname. If the \s-1RSA\s0 algorithm implementation for the selected provider supports it then the digest will be fetched using the properties mdprops. The padding mode must have been set to \fB\s-1RSA_PKCS1_OAEP_PADDING\s0.

\fBEVP_PKEY_CTX_set_rsa_oaep_md() does the same as \fBEVP_PKEY_CTX_set_rsa_oaep_md_name() except that the name of the digest is inferred from the supplied md and it is not possible to specify any properties.

\fBEVP_PKEY_CTX_get_rsa_oaep_md_name() gets the message digest algorithm name used in \s-1RSA OAEP\s0 and stores it in the buffer name which is of size namelen. The padding mode must have been set to \fB\s-1RSA_PKCS1_OAEP_PADDING\s0. The buffer should be sufficiently large for any expected digest algorithm names or the function will fail.

\fBEVP_PKEY_CTX_get_rsa_oaep_md() does the same as \fBEVP_PKEY_CTX_get_rsa_oaep_md_name() except that it returns a pointer to an \s-1EVP_MD\s0 object instead. Note that only known, built-in \s-1EVP_MD\s0 objects will be returned. The \s-1EVP_MD\s0 object may be \s-1NULL\s0 if the digest is not one of these (such as a digest only implemented in a third party provider).

\fBEVP_PKEY_CTX_set0_rsa_oaep_label() sets the \s-1RSA OAEP\s0 label to binary data \fIlabel and its length in bytes to len. If label is \s-1NULL\s0 or len is 0, the label is cleared. The library takes ownership of the label so the caller should not free the original memory pointed to by label. The padding mode must have been set to \s-1RSA_PKCS1_OAEP_PADDING\s0.

\fBEVP_PKEY_CTX_get0_rsa_oaep_label() gets the \s-1RSA OAEP\s0 label to \fIlabel. The return value is the label length. The padding mode must have been set to \s-1RSA_PKCS1_OAEP_PADDING\s0. The resulting pointer is owned by the library and should not be freed by the caller.

\fB\s-1RSA_PKCS1_WITH_TLS_PADDING\s0 is used when decrypting an \s-1RSA\s0 encrypted \s-1TLS\s0 pre-master secret in a \s-1TLS\s0 ClientKeyExchange message. It is the same as \s-1RSA_PKCS1_PADDING\s0 except that it additionally verifies that the result is the correct length and the first two bytes are the protocol version initially requested by the client. If the encrypted content is publicly invalid then the decryption will fail. However, if the padding checks fail then decryption will still appear to succeed but a random \s-1TLS\s0 premaster secret will be returned instead. This padding mode accepts two parameters which can be set using the \fBEVP_PKEY_CTX_set_params\|(3) function. These are \s-1OSSL_ASYM_CIPHER_PARAM_TLS_CLIENT_VERSION\s0 and \s-1OSSL_ASYM_CIPHER_PARAM_TLS_NEGOTIATED_VERSION,\s0 both of which are expected to be unsigned integers. Normally only the first of these will be set and represents the \s-1TLS\s0 protocol version that was first requested by the client (e.g. 0x0303 for TLSv1.2, 0x0302 for TLSv1.1 etc). Historically some buggy clients would use the negotiated protocol version instead of the protocol version first requested. If this behaviour should be tolerated then \s-1OSSL_ASYM_CIPHER_PARAM_TLS_NEGOTIATED_VERSION\s0 should be set to the actual negotiated protocol version. Otherwise it should be left unset.

"\s-1DSA\s0 parameters"
Subsection "DSA parameters" \fBEVP_PKEY_CTX_set_dsa_paramgen_bits() sets the number of bits used for \s-1DSA\s0 parameter generation to nbits. If not specified, 2048 is used.

\fBEVP_PKEY_CTX_set_dsa_paramgen_q_bits() sets the number of bits in the subprime parameter q for \s-1DSA\s0 parameter generation to qbits. If not specified, 224 is used. If a digest function is specified below, this parameter is ignored and instead, the number of bits in q matches the size of the digest.

\fBEVP_PKEY_CTX_set_dsa_paramgen_md() sets the digest function used for \s-1DSA\s0 parameter generation to md. If not specified, one of \s-1SHA-1, SHA-224,\s0 or \s-1SHA-256\s0 is selected to match the bit length of q above.

\fBEVP_PKEY_CTX_set_dsa_paramgen_md_props() sets the digest function used for \s-1DSA\s0 parameter generation using md_name and md_properties to retrieve the digest from a provider. If not specified, md_name will be set to one of \s-1SHA-1, SHA-224,\s0 or \s-1SHA-256\s0 depending on the bit length of q above. md_properties is a property query string that has a default value of '' if not specified.

\fBEVP_PKEY_CTX_set_dsa_paramgen_gindex() sets the gindex used by the generator G. The default value is -1 which uses unverifiable g, otherwise a positive value uses verifiable g. This value must be saved if key validation of g is required, since it is not part of a persisted key.

\fBEVP_PKEY_CTX_set_dsa_paramgen_seed() sets the seed to use for generation rather than using a randomly generated value for the seed. This is useful for testing purposes only and can fail if the seed does not produce primes for both p & q on its first iteration. This value must be saved if key validation of p, q, and verifiable g are required, since it is not part of a persisted key.

\fBEVP_PKEY_CTX_set_dsa_paramgen_type() sets the generation type to use \s-1FIPS186-4\s0 generation if name is \*(L"fips186_4\*(R", or \s-1FIPS186-2\s0 generation if name is \*(L"fips186_2\*(R". The default value for the default provider is \*(L"fips186_2\*(R". The default value for the \s-1FIPS\s0 provider is \*(L"fips186_4\*(R".

"\s-1DH\s0 parameters"
Subsection "DH parameters" \fBEVP_PKEY_CTX_set_dh_paramgen_prime_len() sets the length of the \s-1DH\s0 prime parameter p for \s-1DH\s0 parameter generation. If this function is not called then 2048 is used. Only accepts lengths greater than or equal to 256.

\fBEVP_PKEY_CTX_set_dh_paramgen_subprime_len() sets the length of the \s-1DH\s0 optional subprime parameter q for \s-1DH\s0 parameter generation. The default is 256 if the prime is at least 2048 bits long or 160 otherwise. The \s-1DH\s0 paramgen type must have been set to \*(L"fips186_4\*(R".

\fBEVP_PKEY_CTX_set_dh_paramgen_generator() sets \s-1DH\s0 generator to gen for \s-1DH\s0 parameter generation. If not specified 2 is used.

\fBEVP_PKEY_CTX_set_dh_paramgen_type() sets the key type for \s-1DH\s0 parameter generation. The supported parameters are:

"\s-1DH_PARAMGEN_TYPE_GROUP\s0" 4
Item "DH_PARAMGEN_TYPE_GROUP" Use a named group. If only the safe prime parameter p is set this can be used to select a ffdhe safe prime group of the correct size.
"\s-1DH_PARAMGEN_TYPE_FIPS_186_4\s0" 4
Item "DH_PARAMGEN_TYPE_FIPS_186_4" \s-1FIPS186-4 FFC\s0 parameter generator.
"\s-1DH_PARAMGEN_TYPE_FIPS_186_2\s0" 4
Item "DH_PARAMGEN_TYPE_FIPS_186_2" \s-1FIPS186-2 FFC\s0 parameter generator (X9.42 \s-1DH\s0).
"\s-1DH_PARAMGEN_TYPE_GENERATOR\s0" 4
Item "DH_PARAMGEN_TYPE_GENERATOR" Uses a safe prime generator g (PKCS#3 format).

The default in the default provider is \s-1DH_PARAMGEN_TYPE_GENERATOR\s0 for the \*(L"\s-1DH\*(R"\s0 keytype, and \s-1DH_PARAMGEN_TYPE_FIPS_186_2\s0 for the \*(L"\s-1DHX\*(R"\s0 keytype. In the \s-1FIPS\s0 provider the default value is \s-1DH_PARAMGEN_TYPE_GROUP\s0 for the \*(L"\s-1DH\*(R"\s0 keytype and <\s-1DH_PARAMGEN_TYPE_FIPS_186_4\s0 for the \*(L"\s-1DHX\*(R"\s0 keytype.

\fBEVP_PKEY_CTX_set_dh_paramgen_gindex() sets the gindex used by the generator G. The default value is -1 which uses unverifiable g, otherwise a positive value uses verifiable g. This value must be saved if key validation of g is required, since it is not part of a persisted key.

\fBEVP_PKEY_CTX_set_dh_paramgen_seed() sets the seed to use for generation rather than using a randomly generated value for the seed. This is useful for testing purposes only and can fail if the seed does not produce primes for both p & q on its first iteration. This value must be saved if key validation of p, q, and verifiable g are required, since it is not part of a persisted key.

\fBEVP_PKEY_CTX_set_dh_pad() sets the \s-1DH\s0 padding mode. If pad is 1 the shared secret is padded with zeros up to the size of the \s-1DH\s0 prime p. If pad is zero (the default) then no padding is performed.

\fBEVP_PKEY_CTX_set_dh_nid() sets the \s-1DH\s0 parameters to values corresponding to \fInid as defined in \s-1RFC7919\s0 or \s-1RFC3526.\s0 The nid parameter must be \fBNID_ffdhe2048, NID_ffdhe3072, NID_ffdhe4096, NID_ffdhe6144, \fBNID_ffdhe8192, NID_modp_1536, NID_modp_2048, NID_modp_3072, \fBNID_modp_4096, NID_modp_6144, NID_modp_8192 or NID_undef to clear the stored value. This function can be called during parameter or key generation. The nid parameter and the rfc5114 parameter are mutually exclusive.

\fBEVP_PKEY_CTX_set_dh_rfc5114() and EVP_PKEY_CTX_set_dhx_rfc5114() both set the \s-1DH\s0 parameters to the values defined in \s-1RFC5114.\s0 The rfc5114 parameter must be 1, 2 or 3 corresponding to \s-1RFC5114\s0 sections 2.1, 2.2 and 2.3. or 0 to clear the stored value. This macro can be called during parameter generation. The \fIctx must have a key type of \s-1EVP_PKEY_DHX\s0. The rfc5114 parameter and the nid parameter are mutually exclusive.

"\s-1DH\s0 key derivation function parameters"
Subsection "DH key derivation function parameters" Note that all of the following functions require that the ctx parameter has a private key type of \s-1EVP_PKEY_DHX\s0. When using key derivation, the output of \fBEVP_PKEY_derive() is the output of the \s-1KDF\s0 instead of the \s-1DH\s0 shared secret. The \s-1KDF\s0 output is typically used as a Key Encryption Key (\s-1KEK\s0) that in turn encrypts a Content Encryption Key (\s-1CEK\s0).

\fBEVP_PKEY_CTX_set_dh_kdf_type() sets the key derivation function type to kdf for \s-1DH\s0 key derivation. Possible values are \s-1EVP_PKEY_DH_KDF_NONE\s0 and \fB\s-1EVP_PKEY_DH_KDF_X9_42\s0 which uses the key derivation specified in \s-1RFC2631\s0 (based on the keying algorithm described in X9.42). When using key derivation, the kdf_oid, kdf_md and kdf_outlen parameters must also be specified.

\fBEVP_PKEY_CTX_get_dh_kdf_type() gets the key derivation function type for ctx used for \s-1DH\s0 key derivation. Possible values are \s-1EVP_PKEY_DH_KDF_NONE\s0 and \fB\s-1EVP_PKEY_DH_KDF_X9_42\s0.

\fBEVP_PKEY_CTX_set0_dh_kdf_oid() sets the key derivation function object identifier to oid for \s-1DH\s0 key derivation. This \s-1OID\s0 should identify the algorithm to be used with the Content Encryption Key. The library takes ownership of the object identifier so the caller should not free the original memory pointed to by oid.

\fBEVP_PKEY_CTX_get0_dh_kdf_oid() gets the key derivation function oid for ctx used for \s-1DH\s0 key derivation. The resulting pointer is owned by the library and should not be freed by the caller.

\fBEVP_PKEY_CTX_set_dh_kdf_md() sets the key derivation function message digest to \fImd for \s-1DH\s0 key derivation. Note that \s-1RFC2631\s0 specifies that this digest should be \s-1SHA1\s0 but OpenSSL tolerates other digests.

\fBEVP_PKEY_CTX_get_dh_kdf_md() gets the key derivation function message digest for \fIctx used for \s-1DH\s0 key derivation.

\fBEVP_PKEY_CTX_set_dh_kdf_outlen() sets the key derivation function output length to len for \s-1DH\s0 key derivation.

\fBEVP_PKEY_CTX_get_dh_kdf_outlen() gets the key derivation function output length for ctx used for \s-1DH\s0 key derivation.

\fBEVP_PKEY_CTX_set0_dh_kdf_ukm() sets the user key material to ukm and its length to len for \s-1DH\s0 key derivation. This parameter is optional and corresponds to the partyAInfo field in \s-1RFC2631\s0 terms. The specification requires that it is 512 bits long but this is not enforced by OpenSSL. The library takes ownership of the user key material so the caller should not free the original memory pointed to by ukm.

\fBEVP_PKEY_CTX_get0_dh_kdf_ukm() gets the user key material for ctx. The return value is the user key material length. The resulting pointer is owned by the library and should not be freed by the caller.

"\s-1EC\s0 parameters"
Subsection "EC parameters" Use EVP_PKEY_CTX_set_group_name() (described above) to set the curve name to \fIname for parameter and key generation.

\fBEVP_PKEY_CTX_set_ec_paramgen_curve_nid() does the same as \fBEVP_PKEY_CTX_set_group_name(), but is specific to \s-1EC\s0 and uses a nid rather than a name string.

For \s-1EC\s0 parameter generation, one of EVP_PKEY_CTX_set_group_name() or EVP_PKEY_CTX_set_ec_paramgen_curve_nid() must be called or an error occurs because there is no default curve. These function can also be called to set the curve explicitly when generating an \s-1EC\s0 key.

\fBEVP_PKEY_CTX_get_group_name() (described above) can be used to obtain the curve name that's currently set with ctx.

\fBEVP_PKEY_CTX_set_ec_param_enc() sets the \s-1EC\s0 parameter encoding to param_enc when generating \s-1EC\s0 parameters or an \s-1EC\s0 key. The encoding can be \fB\s-1OPENSSL_EC_EXPLICIT_CURVE\s0 for explicit parameters (the default in versions of OpenSSL before 1.1.0) or \s-1OPENSSL_EC_NAMED_CURVE\s0 to use named curve form. For maximum compatibility the named curve form should be used. Note: the \fB\s-1OPENSSL_EC_NAMED_CURVE\s0 value was added in OpenSSL 1.1.0; previous versions should use 0 instead.

"\s-1ECDH\s0 parameters"
Subsection "ECDH parameters" \fBEVP_PKEY_CTX_set_ecdh_cofactor_mode() sets the cofactor mode to cofactor_mode for \s-1ECDH\s0 key derivation. Possible values are 1 to enable cofactor key derivation, 0 to disable it and -1 to clear the stored cofactor mode and fallback to the private key cofactor mode.

\fBEVP_PKEY_CTX_get_ecdh_cofactor_mode() returns the cofactor mode for ctx used for \s-1ECDH\s0 key derivation. Possible values are 1 when cofactor key derivation is enabled and 0 otherwise.

"\s-1ECDH\s0 key derivation function parameters"
Subsection "ECDH key derivation function parameters" \fBEVP_PKEY_CTX_set_ecdh_kdf_type() sets the key derivation function type to \fIkdf for \s-1ECDH\s0 key derivation. Possible values are \s-1EVP_PKEY_ECDH_KDF_NONE\s0 and \s-1EVP_PKEY_ECDH_KDF_X9_63\s0 which uses the key derivation specified in X9.63. When using key derivation, the kdf_md and kdf_outlen parameters must also be specified.

\fBEVP_PKEY_CTX_get_ecdh_kdf_type() returns the key derivation function type for \fIctx used for \s-1ECDH\s0 key derivation. Possible values are \fB\s-1EVP_PKEY_ECDH_KDF_NONE\s0 and \s-1EVP_PKEY_ECDH_KDF_X9_63\s0.

\fBEVP_PKEY_CTX_set_ecdh_kdf_md() sets the key derivation function message digest to md for \s-1ECDH\s0 key derivation. Note that X9.63 specifies that this digest should be \s-1SHA1\s0 but OpenSSL tolerates other digests.

\fBEVP_PKEY_CTX_get_ecdh_kdf_md() gets the key derivation function message digest for ctx used for \s-1ECDH\s0 key derivation.

\fBEVP_PKEY_CTX_set_ecdh_kdf_outlen() sets the key derivation function output length to len for \s-1ECDH\s0 key derivation.

\fBEVP_PKEY_CTX_get_ecdh_kdf_outlen() gets the key derivation function output length for ctx used for \s-1ECDH\s0 key derivation.

\fBEVP_PKEY_CTX_set0_ecdh_kdf_ukm() sets the user key material to ukm for \s-1ECDH\s0 key derivation. This parameter is optional and corresponds to the shared info in X9.63 terms. The library takes ownership of the user key material so the caller should not free the original memory pointed to by ukm.

\fBEVP_PKEY_CTX_get0_ecdh_kdf_ukm() gets the user key material for ctx. The return value is the user key material length. The resulting pointer is owned by the library and should not be freed by the caller.

"Other parameters"
Subsection "Other parameters" \fBEVP_PKEY_CTX_set1_id(), EVP_PKEY_CTX_get1_id() and EVP_PKEY_CTX_get1_id_len() are used to manipulate the special identifier field for specific signature algorithms such as \s-1SM2.\s0 The EVP_PKEY_CTX_set1_id() sets an \s-1ID\s0 pointed by id with the length id_len to the library. The library takes a copy of the id so that the caller can safely free the original memory pointed to by id. \fBEVP_PKEY_CTX_get1_id_len() returns the length of the \s-1ID\s0 set via a previous call to EVP_PKEY_CTX_set1_id(). The length is usually used to allocate adequate memory for further calls to EVP_PKEY_CTX_get1_id(). EVP_PKEY_CTX_get1_id() returns the previously set \s-1ID\s0 value to caller in id. The caller should allocate adequate memory space for the id before calling EVP_PKEY_CTX_get1_id().

\fBEVP_PKEY_CTX_set_kem_op() sets the \s-1KEM\s0 operation to run. This can be set after \fBEVP_PKEY_encapsulate_init() or EVP_PKEY_decapsulate_init() to select the kem operation. \s-1RSA\s0 is the only key type that supports encapsulation currently, and as there is no default operation for the \s-1RSA\s0 type, this function must be called before EVP_PKEY_encapsulate() or EVP_PKEY_decapsulate().

"RETURN VALUES"
Header "RETURN VALUES" All other functions described on this page return a positive value for success and 0 or a negative value for failure. In particular a return value of -2 indicates the operation is not supported by the public key algorithm.
"SEE ALSO"
Header "SEE ALSO" \fBEVP_PKEY_CTX_set_params\|(3), \fBEVP_PKEY_CTX_new\|(3), \fBEVP_PKEY_encrypt\|(3), \fBEVP_PKEY_decrypt\|(3), \fBEVP_PKEY_sign\|(3), \fBEVP_PKEY_verify\|(3), \fBEVP_PKEY_verify_recover\|(3), \fBEVP_PKEY_derive\|(3), \fBEVP_PKEY_keygen\|(3) \fBEVP_PKEY_encapsulate\|(3) \fBEVP_PKEY_decapsulate\|(3)
"HISTORY"
Header "HISTORY" \fBEVP_PKEY_CTX_get_rsa_oaep_md_name(), EVP_PKEY_CTX_get_rsa_mgf1_md_name(), \fBEVP_PKEY_CTX_set_rsa_mgf1_md_name(), EVP_PKEY_CTX_set_rsa_oaep_md_name(), \fBEVP_PKEY_CTX_set_dsa_paramgen_md_props(), EVP_PKEY_CTX_set_dsa_paramgen_gindex(), \fBEVP_PKEY_CTX_set_dsa_paramgen_type(), EVP_PKEY_CTX_set_dsa_paramgen_seed(), \fBEVP_PKEY_CTX_set_group_name() and EVP_PKEY_CTX_get_group_name() were added in OpenSSL 3.0.

The EVP_PKEY_CTX_set1_id(), EVP_PKEY_CTX_get1_id() and \fBEVP_PKEY_CTX_get1_id_len() macros were added in 1.1.1, other functions were added in OpenSSL 1.0.0.

In OpenSSL 1.1.1 and below the functions were mostly macros. From OpenSSL 3.0 they are all functions.

\fBEVP_PKEY_CTX_set_rsa_keygen_pubexp(), EVP_PKEY_CTX_get0_dh_kdf_ukm(), and EVP_PKEY_CTX_get0_ecdh_kdf_ukm() were deprecated in OpenSSL 3.0.

"COPYRIGHT"
Header "COPYRIGHT" Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.