| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_KDF-SS - The Single Step / One Step EVP_KDF implementation
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| 6 |
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| 7 | =head1 DESCRIPTION
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| 8 |
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| 9 | The EVP_KDF-SS algorithm implements the Single Step key derivation function (SSKDF).
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| 10 | SSKDF derives a key using input such as a shared secret key (that was generated
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| 11 | during the execution of a key establishment scheme) and fixedinfo.
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| 12 | SSKDF is also informally referred to as 'Concat KDF'.
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| 13 |
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| 14 | =head2 Auxiliary function
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| 15 |
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| 16 | The implementation uses a selectable auxiliary function H, which can be one of:
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| 17 |
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| 18 | =over 4
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| 19 |
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| 20 | =item B<H(x) = hash(x, digest=md)>
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| 21 |
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| 22 | =item B<H(x) = HMAC_hash(x, key=salt, digest=md)>
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| 23 |
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| 24 | =item B<H(x) = KMACxxx(x, key=salt, custom="KDF", outlen=mac_size)>
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| 25 |
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| 26 | =back
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| 27 |
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| 28 | Both the HMAC and KMAC implementations set the key using the 'salt' value.
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| 29 | The hash and HMAC also require the digest to be set.
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| 30 |
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| 31 | =head2 Identity
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| 32 |
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| 33 | "SSKDF" is the name for this implementation; it
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| 34 | can be used with the EVP_KDF_fetch() function.
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| 35 |
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| 36 | =head2 Supported parameters
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| 37 |
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| 38 | The supported parameters are:
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| 39 |
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| 40 | =over 4
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| 41 |
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| 42 | =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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| 43 |
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| 44 | =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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| 45 |
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| 46 | This parameter is ignored for KMAC.
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| 47 |
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| 48 | =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
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| 49 |
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| 50 | =item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
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| 51 |
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| 52 | =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
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| 53 |
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| 54 | These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
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| 55 |
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| 56 | =item "key" (B<OSSL_KDF_PARAM_SECRET>) <octet string>
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| 57 |
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| 58 | This parameter set the shared secret that is used for key derivation.
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| 59 |
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| 60 | =item "info" (B<OSSL_KDF_PARAM_INFO>) <octet string>
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| 61 |
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| 62 | This parameter sets an optional value for fixedinfo, also known as otherinfo.
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| 63 |
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| 64 | =back
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| 65 |
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| 66 | =head1 NOTES
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| 67 |
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| 68 | A context for SSKDF can be obtained by calling:
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| 69 |
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| 70 | EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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| 71 | EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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| 72 |
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| 73 | The output length of an SSKDF is specified via the I<keylen>
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| 74 | parameter to the L<EVP_KDF_derive(3)> function.
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| 75 |
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| 76 | =head1 EXAMPLES
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| 77 |
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| 78 | This example derives 10 bytes using H(x) = SHA-256, with the secret key "secret"
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| 79 | and fixedinfo value "label":
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| 80 |
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| 81 | EVP_KDF *kdf;
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| 82 | EVP_KDF_CTX *kctx;
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| 83 | unsigned char out[10];
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| 84 | OSSL_PARAM params[4], *p = params;
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| 85 |
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| 86 | kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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| 87 | kctx = EVP_KDF_CTX_new(kdf);
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| 88 | EVP_KDF_free(kdf);
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| 89 |
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| 90 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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| 91 | SN_sha256, strlen(SN_sha256));
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| 92 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
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| 93 | "secret", (size_t)6);
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| 94 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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| 95 | "label", (size_t)5);
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| 96 | *p = OSSL_PARAM_construct_end();
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| 97 | if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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| 98 | error("EVP_KDF_derive");
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| 99 | }
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| 100 |
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| 101 | EVP_KDF_CTX_free(kctx);
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| 102 |
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| 103 | This example derives 10 bytes using H(x) = HMAC(SHA-256), with the secret key "secret",
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| 104 | fixedinfo value "label" and salt "salt":
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| 105 |
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| 106 | EVP_KDF *kdf;
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| 107 | EVP_KDF_CTX *kctx;
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| 108 | unsigned char out[10];
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| 109 | OSSL_PARAM params[6], *p = params;
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| 110 |
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| 111 | kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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| 112 | kctx = EVP_KDF_CTX_new(kdf);
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| 113 | EVP_KDF_free(kdf);
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| 114 |
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| 115 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
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| 116 | SN_hmac, strlen(SN_hmac));
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| 117 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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| 118 | SN_sha256, strlen(SN_sha256));
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| 119 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
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| 120 | "secret", (size_t)6);
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| 121 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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| 122 | "label", (size_t)5);
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| 123 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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| 124 | "salt", (size_t)4);
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| 125 | *p = OSSL_PARAM_construct_end();
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| 126 | if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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| 127 | error("EVP_KDF_derive");
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| 128 | }
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| 129 |
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| 130 | EVP_KDF_CTX_free(kctx);
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| 131 |
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| 132 | This example derives 10 bytes using H(x) = KMAC128(x,salt,outlen), with the secret key "secret"
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| 133 | fixedinfo value "label", salt of "salt" and KMAC outlen of 20:
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| 134 |
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| 135 | EVP_KDF *kdf;
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| 136 | EVP_KDF_CTX *kctx;
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| 137 | unsigned char out[10];
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| 138 | OSSL_PARAM params[6], *p = params;
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| 139 |
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| 140 | kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
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| 141 | kctx = EVP_KDF_CTX_new(kdf);
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| 142 | EVP_KDF_free(kdf);
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| 143 |
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| 144 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
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| 145 | SN_kmac128, strlen(SN_kmac128));
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| 146 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
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| 147 | "secret", (size_t)6);
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| 148 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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| 149 | "label", (size_t)5);
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| 150 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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| 151 | "salt", (size_t)4);
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| 152 | *p++ = OSSL_PARAM_construct_size_t(OSSL_KDF_PARAM_MAC_SIZE, (size_t)20);
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| 153 | *p = OSSL_PARAM_construct_end();
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| 154 | if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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| 155 | error("EVP_KDF_derive");
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| 156 | }
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| 157 |
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| 158 | EVP_KDF_CTX_free(kctx);
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| 159 |
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| 160 | =head1 CONFORMING TO
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| 161 |
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| 162 | NIST SP800-56Cr1.
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| 163 |
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| 164 | =head1 SEE ALSO
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| 165 |
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| 166 | L<EVP_KDF(3)>,
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| 167 | L<EVP_KDF_CTX_new(3)>,
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| 168 | L<EVP_KDF_CTX_free(3)>,
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| 169 | L<EVP_KDF_CTX_set_params(3)>,
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| 170 | L<EVP_KDF_CTX_get_kdf_size(3)>,
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| 171 | L<EVP_KDF_derive(3)>,
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| 172 | L<EVP_KDF(3)/PARAMETERS>
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| 173 |
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| 174 | =head1 HISTORY
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| 175 |
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| 176 | This functionality was added in OpenSSL 3.0.
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| 177 |
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| 178 | =head1 COPYRIGHT
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| 179 |
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| 180 | Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved. Copyright
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| 181 | (c) 2019, Oracle and/or its affiliates. All rights reserved.
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| 182 |
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| 183 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 184 | this file except in compliance with the License. You can obtain a copy
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| 185 | in the file LICENSE in the source distribution or at
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| 186 | L<https://www.openssl.org/source/license.html>.
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| 187 |
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| 188 | =cut
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