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Title "EVP_PKEY-EC 7"
way too many mistakes in technical documents.
The following KeyGen/Gettable/Import/Export types are available for the built-in \s-1EC\s0 algorithm: Item "group (OSSL_PKEY_PARAM_GROUP_NAME) <UTF8 string>" The curve name. Item "field-type (OSSL_PKEY_PARAM_EC_FIELD_TYPE) <UTF8 string>" The value should be either \*(L"prime-field\*(R" or \*(L"characteristic-two-field\*(R", which correspond to prime field Fp and binary field F2^m. Item "p (OSSL_PKEY_PARAM_EC_P) <unsigned integer>" For a curve over Fp p is the prime for the field. For a curve over F2^m p represents the irreducible polynomial - each bit represents a term in the polynomial. Therefore, there will either be three or five bits set dependent on whether the polynomial is a trinomial or a pentanomial. Item "a (OSSL_PKEY_PARAM_EC_A) <unsigned integer>"
0 Item "b (OSSL_PKEY_PARAM_EC_B) <unsigned integer>" Item "seed (OSSL_PKEY_PARAM_EC_SEED) <octet string>"
\fIa and b represents the coefficients of the curve For Fp: y^2 mod p = x^3 +ax + b mod p \s-1OR\s0 For F2^m: y^2 + xy = x^3 + ax^2 + b .Sp \fIseed is an optional value that is for information purposes only. It represents the random number seed used to generate the coefficient b from a random number. Item "generator (OSSL_PKEY_PARAM_EC_GENERATOR) <octet string>"
0 Item "order (OSSL_PKEY_PARAM_EC_ORDER) <unsigned integer>" Item "cofactor (OSSL_PKEY_PARAM_EC_COFACTOR) <unsigned integer>"
The generator is a well defined point on the curve chosen for cryptographic operations. The encoding conforms with Sec. 2.3.3 of the \s-1SECG SEC 1\s0 (\*(L"Elliptic Curve Cryptography\*(R") standard. See EC_POINT_oct2point(). Integers used for point multiplications will be between 0 and \fIorder - 1. \fIcofactor is an optional value. \fIorder multiplied by the cofactor gives the number of points on the curve. Item "decoded-from-explicit (OSSL_PKEY_PARAM_EC_DECODED_FROM_EXPLICIT_PARAMS) <integer>" Gets a flag indicating whether the key or parameters were decoded from explicit curve parameters. Set to 1 if so or 0 if a named curve was used. Item "use-cofactor-flag (OSSL_PKEY_PARAM_USE_COFACTOR_ECDH) <integer>" Enable Cofactor \s-1DH\s0 (\s-1ECC CDH\s0) if this value is 1, otherwise it uses normal \s-1EC DH\s0 if the value is zero. The cofactor variant multiplies the shared secret by the \s-1EC\s0 curve's cofactor (note for some curves the cofactor is 1). .Sp See also \s-1EVP_KEYEXCH-ECDH\s0\|(7) for the related \fB\s-1OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE\s0 parameter that can be set on a per-operation basis. Item "encoding (OSSL_PKEY_PARAM_EC_ENCODING) <UTF8 string>" Set the format used for serializing the \s-1EC\s0 group parameters. Valid values are \*(L"explicit\*(R" or \*(L"named_curve\*(R". The default value is \*(L"named_curve\*(R". Item "point-format (OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMAT) <UTF8 string>" Sets or gets the point_conversion_form for the key. For a description of point_conversion_forms please see EC_POINT_new\|(3). Valid values are \*(L"uncompressed\*(R" or \*(L"compressed\*(R". The default value is \*(L"uncompressed\*(R". Item "group-check (OSSL_PKEY_PARAM_EC_GROUP_CHECK_TYPE) <UTF8 string>" Sets or Gets the type of group check done when EVP_PKEY_param_check() is called. Valid values are \*(L"default\*(R", \*(L"named\*(R" and \*(L"named-nist\*(R". The \*(L"named\*(R" type checks that the domain parameters match the inbuilt curve parameters, \*(L"named-nist\*(R" is similar but also checks that the named curve is a nist curve. The \*(L"default\*(R" type does domain parameter validation for the OpenSSL default provider, but is equivalent to \*(L"named-nist\*(R" for the OpenSSL \s-1FIPS\s0 provider. Item "include-public (OSSL_PKEY_PARAM_EC_INCLUDE_PUBLIC) <integer>" Setting this value to 0 indicates that the public key should not be included when encoding the private key. The default value of 1 will include the public key. Item "pub (OSSL_PKEY_PARAM_PUB_KEY) <octet string>" The public key value in encoded \s-1EC\s0 point format conforming to Sec. 2.3.3 and 2.3.4 of the \s-1SECG SEC 1\s0 (\*(L"Elliptic Curve Cryptography\*(R") standard. This parameter is used when importing or exporting the public key value with the \fBEVP_PKEY_fromdata() and EVP_PKEY_todata() functions. .Sp Note, in particular, that the choice of point compression format used for encoding the exported value via EVP_PKEY_todata() depends on the underlying provider implementation. Before OpenSSL 3.0.8, the implementation of providers included with OpenSSL always opted for an encoding in compressed format, unconditionally. Since OpenSSL 3.0.8, the implementation has been changed to honor the \fB\s-1OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMAT\s0 parameter, if set, or to default to uncompressed format. Item "priv (OSSL_PKEY_PARAM_PRIV_KEY) <unsigned integer>" The private key value. Item "encoded-pub-key (OSSL_PKEY_PARAM_ENCODED_PUBLIC_KEY) <octet string>" Used for getting and setting the encoding of an \s-1EC\s0 public key. The public key is expected to be a point conforming to Sec. 2.3.4 of the \s-1SECG SEC 1\s0 (\*(L"Elliptic Curve Cryptography\*(R") standard. Item "qx (OSSL_PKEY_PARAM_EC_PUB_X) <unsigned integer>" Used for getting the \s-1EC\s0 public key X component. Item "qy (OSSL_PKEY_PARAM_EC_PUB_Y) <unsigned integer>" Used for getting the \s-1EC\s0 public key Y component. Item "default-digest (OSSL_PKEY_PARAM_DEFAULT_DIGEST) <UTF8 string>" Getter that returns the default digest name. (Currently returns \*(L"\s-1SHA256\*(R"\s0 as of OpenSSL 3.0).
The following Gettable types are also available for the built-in \s-1EC\s0 algorithm: Item "basis-type (OSSL_PKEY_PARAM_EC_CHAR2_TYPE) <UTF8 string>" Supports the values \*(L"tpBasis\*(R" for a trinomial or \*(L"ppBasis\*(R" for a pentanomial. This field is only used for a binary field F2^m. Item "m (OSSL_PKEY_PARAM_EC_CHAR2_M) <integer>"
0 Item "tp (OSSL_PKEY_PARAM_EC_CHAR2_TP_BASIS) <integer>" Item "k1 (OSSL_PKEY_PARAM_EC_CHAR2_PP_K1) <integer>" Item "k2 (OSSL_PKEY_PARAM_EC_CHAR2_PP_K2) <integer>" Item "k3 (OSSL_PKEY_PARAM_EC_CHAR2_PP_K3) <integer>"
These fields are only used for a binary field F2^m. \fIm is the degree of the binary field. .Sp \fItp is the middle bit of a trinomial so its value must be in the range m > tp > 0. .Sp \fIk1, k2 and k3 are used to get the middle bits of a pentanomial such that m > k3 > k2 > k1 > 0
For \s-1EC\s0 keys, EVP_PKEY_param_check_quick\|(3) is equivalent to \fBEVP_PKEY_param_check\|(3).
For \s-1EC\s0 keys, EVP_PKEY_public_check\|(3) and EVP_PKEY_public_check_quick\|(3) conform to SP800-56Ar3 \s-1ECC\s0 Full Public-Key Validation and \fI\s-1ECC\s0 Partial Public-Key Validation respectively.
For \s-1EC\s0 Keys, EVP_PKEY_private_check\|(3) and EVP_PKEY_pairwise_check\|(3) conform to SP800-56Ar3 Private key validity and \fIOwner Assurance of Pair-wise Consistency respectively.
.Vb 2 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "EC", NULL); .Ve
An \s-1EVP_PKEY\s0 \s-1ECDSA\s0 or \s-1ECDH\s0 key can be generated with a \*(L"P-256\*(R" named group by calling:
.Vb 1 pkey = EVP_EC_gen("P-256"); .Ve
or like this:
.Vb 4 EVP_PKEY *key = NULL; OSSL_PARAM params[2]; EVP_PKEY_CTX *gctx = EVP_PKEY_CTX_new_from_name(NULL, "EC", NULL); \& EVP_PKEY_keygen_init(gctx); \& params[0] = OSSL_PARAM_construct_utf8_string(OSSL_PKEY_PARAM_GROUP_NAME, "P-256", 0); params[1] = OSSL_PARAM_construct_end(); EVP_PKEY_CTX_set_params(gctx, params); \& EVP_PKEY_generate(gctx, &key); \& EVP_PKEY_print_private(bio_out, key, 0, NULL); ... EVP_PKEY_free(key); EVP_PKEY_CTX_free(gctx); .Ve
An \s-1EVP_PKEY\s0 \s-1EC CDH\s0 (Cofactor Diffie-Hellman) key can be generated with a \*(L"K-571\*(R" named group by calling:
.Vb 5 int use_cdh = 1; EVP_PKEY *key = NULL; OSSL_PARAM params[3]; EVP_PKEY_CTX *gctx = EVP_PKEY_CTX_new_from_name(NULL, "EC", NULL); \& EVP_PKEY_keygen_init(gctx); \& params[0] = OSSL_PARAM_construct_utf8_string(OSSL_PKEY_PARAM_GROUP_NAME, "K-571", 0); /* * This curve has a cofactor that is not 1 - so setting CDH mode changes * the behaviour. For many curves the cofactor is 1 - so setting this has * no effect. */ params[1] = OSSL_PARAM_construct_int(OSSL_PKEY_PARAM_USE_COFACTOR_ECDH, &use_cdh); params[2] = OSSL_PARAM_construct_end(); EVP_PKEY_CTX_set_params(gctx, params); \& EVP_PKEY_generate(gctx, &key); EVP_PKEY_print_private(bio_out, key, 0, NULL); ... EVP_PKEY_free(key); EVP_PKEY_CTX_free(gctx); .Ve
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>.