{ "content": [ { "type": "text", "text": "# EVP_KDF-X942-ASN1(7ssl) (man)\n\n## NAME\n\nEVPKDF-X942-ASN1 - The X9.42-2003 asn1 EVPKDF implementation\n\n## DESCRIPTION\n\nThe EVPKDF-X942-ASN1 algorithm implements the key derivation function X942KDF-ASN1. It is\nused by DH KeyAgreement, to derive a key using input such as a shared secret key and other\ninfo. The other info is DER encoded data that contains a 32 bit counter as well as optional\nfields for \"partyu-info\", \"partyv-info\", \"supp-pubinfo\" and \"supp-privinfo\". This kdf is\nused by Cryptographic Message Syntax (CMS).\n\n## Sections\n\n- **NAME**\n- **DESCRIPTION** (2 subsections)\n- **NOTES**\n- **EXAMPLES**\n- **CONFORMING TO**\n- **SEE ALSO**\n- **HISTORY**\n- **COPYRIGHT**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n" } ], "structuredContent": { "command": "EVP_KDF-X942-ASN1", "section": "7ssl", "mode": "man", "summary": "EVPKDF-X942-ASN1 - The X9.42-2003 asn1 EVPKDF implementation", "synopsis": null, "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [], "examples": [ "This example derives 24 bytes, with the secret key \"secret\" and random user keying material:", "EVPKDFCTX *kctx;", "EVPKDFCTX *kctx;", "unsigned char out[192/8];", "unsignred char ukm[64];", "OSSLPARAM params[5], *p = params;", "if (RANDbytes(ukm, sizeof(ukm)) <= 0)", "error(\"RANDbytes\");", "kdf = EVPKDFfetch(NULL, \"X942KDF\", NULL);", "if (kctx == NULL)", "error(\"EVPKDFfetch\");", "kctx = EVPKDFCTXnew(kdf);", "EVPKDFfree(kdf);", "if (kctx == NULL)", "error(\"EVPKDFCTXnew\");", "*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST, \"SHA256\", 0);", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMSECRET,", "\"secret\", (sizet)6);", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMUKM, ukm, sizeof(ukm));", "*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMCEKALG, \"AES-256-WRAP, 0);", "*p = OSSLPARAMconstructend();", "if (EVPKDFderive(kctx, out, sizeof(out), params) <= 0)", "error(\"EVPKDFderive\");", "EVPKDFCTXfree(kctx);" ], "see_also": [ { "name": "EVPKDF", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/EVPKDF/3/json" }, { "name": "EVPKDFCTXnew", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/EVPKDFCTXnew/3/json" }, { "name": "EVPKDFCTXfree", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/EVPKDFCTXfree/3/json" }, { "name": "EVPKDFCTXsetparams", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/EVPKDFCTXsetparams/3/json" }, { "name": "EVPKDFCTXgetkdfsize", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/EVPKDFCTXgetkdfsize/3/json" }, { "name": "EVPKDFderive", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/EVPKDFderive/3/json" }, { "name": "EVPKDF", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/EVPKDF/3/json" } ], "section_outline": [ { "name": "NAME", "lines": 2, "subsections": [] }, { "name": "DESCRIPTION", "lines": 6, "subsections": [ { "name": "Identity", "lines": 3 }, { "name": "Supported parameters", "lines": 39 } ] }, { "name": "NOTES", "lines": 8, "subsections": [] }, { "name": "EXAMPLES", "lines": 30, "subsections": [] }, { "name": "CONFORMING TO", "lines": 2, "subsections": [] }, { "name": "SEE ALSO", "lines": 3, "subsections": [] }, { "name": "HISTORY", "lines": 2, "subsections": [] }, { "name": "COPYRIGHT", "lines": 9, "subsections": [] } ], "sections": { "NAME": { "content": "EVPKDF-X942-ASN1 - The X9.42-2003 asn1 EVPKDF implementation\n", "subsections": [] }, "DESCRIPTION": { "content": "The EVPKDF-X942-ASN1 algorithm implements the key derivation function X942KDF-ASN1. It is\nused by DH KeyAgreement, to derive a key using input such as a shared secret key and other\ninfo. The other info is DER encoded data that contains a 32 bit counter as well as optional\nfields for \"partyu-info\", \"partyv-info\", \"supp-pubinfo\" and \"supp-privinfo\". This kdf is\nused by Cryptographic Message Syntax (CMS).\n", "subsections": [ { "name": "Identity", "content": "\"X942KDF-ASN1\" or \"X942KDF\" is the name for this implementation; it can be used with the\nEVPKDFfetch() function.\n" }, { "name": "Supported parameters", "content": "The supported parameters are:\n\n\"properties\" (OSSLKDFPARAMPROPERTIES) \n\"digest\" (OSSLKDFPARAMDIGEST) \nThese parameters work as described in \"PARAMETERS\" in EVPKDF(3).\n\n\"key\" (OSSLKDFPARAMKEY) \nThe shared secret used for key derivation. This parameter sets the secret.\n\n\"acvp-info\" (OSSLKDFPARAMX942ACVPINFO) \nThis value should not be used in production and should only be used for ACVP testing. It\nis an optional octet string containing a combined DER encoded blob of any of the optional\nfields related to \"partyu-info\", \"partyv-info\", \"supp-pubinfo\" and \"supp-privinfo\". If it\nis specified then none of these other fields should be used.\n\n\"partyu-info\" (OSSLKDFPARAMX942PARTYUINFO) \nAn optional octet string containing public info contributed by the initiator.\n\n\"ukm\" (OSSLKDFPARAMUKM) \nAn alias for \"partyu-info\". In CMS this is the user keying material.\n\n\"partyv-info\" (OSSLKDFPARAMX942PARTYVINFO) \nAn optional octet string containing public info contributed by the responder.\n\n\"supp-pubinfo\" (OSSLKDFPARAMX942SUPPPUBINFO) \nAn optional octet string containing some additional, mutually-known public information.\nSetting this value also sets \"use-keybits\" to 0.\n\n\"use-keybits\" (OSSLKDFPARAMX942SUPPPRIVINFO) \nThe default value of 1 will use the KEK key length (in bits) as the \"supp-pubinfo\". A\nvalue of 0 disables setting the \"supp-pubinfo\".\n\n\"supp-privinfo\" (OSSLKDFPARAMX942SUPPPRIVINFO) \nAn optional octet string containing some additional, mutually-known private information.\n\n\"cekalg\" (OSSLKDFPARAMCEKALG) \nThis parameter sets the CEK wrapping algorithm name. Valid values are \"AES-128-WRAP\",\n\"AES-192-WRAP\", \"AES-256-WRAP\" and \"DES3-WRAP\".\n" } ] }, "NOTES": { "content": "A context for X942KDF can be obtained by calling:\n\nEVPKDF *kdf = EVPKDFfetch(NULL, \"X942KDF\", NULL);\nEVPKDFCTX *kctx = EVPKDFCTXnew(kdf);\n\nThe output length of an X942KDF is specified via the keylen parameter to the\nEVPKDFderive(3) function.\n", "subsections": [] }, "EXAMPLES": { "content": "This example derives 24 bytes, with the secret key \"secret\" and random user keying material:\n\nEVPKDFCTX *kctx;\nEVPKDFCTX *kctx;\nunsigned char out[192/8];\nunsignred char ukm[64];\nOSSLPARAM params[5], *p = params;\n\nif (RANDbytes(ukm, sizeof(ukm)) <= 0)\nerror(\"RANDbytes\");\n\nkdf = EVPKDFfetch(NULL, \"X942KDF\", NULL);\nif (kctx == NULL)\nerror(\"EVPKDFfetch\");\nkctx = EVPKDFCTXnew(kdf);\nEVPKDFfree(kdf);\nif (kctx == NULL)\nerror(\"EVPKDFCTXnew\");\n\n*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST, \"SHA256\", 0);\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMSECRET,\n\"secret\", (sizet)6);\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMUKM, ukm, sizeof(ukm));\n*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMCEKALG, \"AES-256-WRAP, 0);\n*p = OSSLPARAMconstructend();\nif (EVPKDFderive(kctx, out, sizeof(out), params) <= 0)\nerror(\"EVPKDFderive\");\n\nEVPKDFCTXfree(kctx);\n", "subsections": [] }, "CONFORMING TO": { "content": "ANS1 X9.42-2003 RFC 2631\n", "subsections": [] }, "SEE ALSO": { "content": "EVPKDF(3), EVPKDFCTXnew(3), EVPKDFCTXfree(3), EVPKDFCTXsetparams(3),\nEVPKDFCTXgetkdfsize(3), EVPKDFderive(3), \"PARAMETERS\" in EVPKDF(3)\n", "subsections": [] }, "HISTORY": { "content": "This functionality was added to OpenSSL 3.0.\n", "subsections": [] }, "COPYRIGHT": { "content": "Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.\n\nLicensed under the Apache License 2.0 (the \"License\"). You may not use this file except in\ncompliance with the License. You can obtain a copy in the file LICENSE in the source\ndistribution or at .\n\n\n\n3.0.2 2026-06-02 EVPKDF-X942-ASN1(7SSL)", "subsections": [] } } } }