{ "content": [ { "type": "text", "text": "# EVP_KDF-SS (man)\n\n## NAME\n\nEVPKDF-SS - The Single Step / One Step EVPKDF implementation\n\n## DESCRIPTION\n\nThe EVPKDF-SS algorithm implements the Single Step key derivation function (SSKDF). SSKDF\nderives a key using input such as a shared secret key (that was generated during the\nexecution of a key establishment scheme) and fixedinfo. SSKDF is also informally referred to\nas 'Concat KDF'.\n\n## Sections\n\n- **NAME**\n- **DESCRIPTION** (4 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-SS", "section": "", "mode": "man", "summary": "EVPKDF-SS - The Single Step / One Step EVPKDF implementation", "synopsis": null, "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [], "examples": [ "This example derives 10 bytes using H(x) = SHA-256, with the secret key \"secret\" and", "fixedinfo value \"label\":", "EVPKDF *kdf;", "EVPKDFCTX *kctx;", "unsigned char out[10];", "OSSLPARAM params[4], *p = params;", "kdf = EVPKDFfetch(NULL, \"SSKDF\", NULL);", "kctx = EVPKDFCTXnew(kdf);", "EVPKDFfree(kdf);", "*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST,", "SNsha256, strlen(SNsha256));", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMKEY,", "\"secret\", (sizet)6);", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMINFO,", "\"label\", (sizet)5);", "*p = OSSLPARAMconstructend();", "if (EVPKDFderive(kctx, out, sizeof(out), params) <= 0) {", "error(\"EVPKDFderive\");", "EVPKDFCTXfree(kctx);", "This example derives 10 bytes using H(x) = HMAC(SHA-256), with the secret key \"secret\",", "fixedinfo value \"label\" and salt \"salt\":", "EVPKDF *kdf;", "EVPKDFCTX *kctx;", "unsigned char out[10];", "OSSLPARAM params[6], *p = params;", "kdf = EVPKDFfetch(NULL, \"SSKDF\", NULL);", "kctx = EVPKDFCTXnew(kdf);", "EVPKDFfree(kdf);", "*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMMAC,", "SNhmac, strlen(SNhmac));", "*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST,", "SNsha256, strlen(SNsha256));", "*p++ = OSSLPARAMconstructoctetstring(EVPKDFCTRLSETKEY,", "\"secret\", (sizet)6);", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMINFO,", "\"label\", (sizet)5);", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMSALT,", "\"salt\", (sizet)4);", "*p = OSSLPARAMconstructend();", "if (EVPKDFderive(kctx, out, sizeof(out), params) <= 0) {", "error(\"EVPKDFderive\");", "EVPKDFCTXfree(kctx);", "This example derives 10 bytes using H(x) = KMAC128(x,salt,outlen), with the secret key", "\"secret\" fixedinfo value \"label\", salt of \"salt\" and KMAC outlen of 20:", "EVPKDF *kdf;", "EVPKDFCTX *kctx;", "unsigned char out[10];", "OSSLPARAM params[7], *p = params;", "kdf = EVPKDFfetch(NULL, \"SSKDF\", NULL);", "kctx = EVPKDFCTXnew(kdf);", "EVPKDFfree(kdf);", "*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMMAC,", "SNkmac128, strlen(SNkmac128));", "*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST,", "SNsha256, strlen(SNsha256));", "*p++ = OSSLPARAMconstructoctetstring(EVPKDFCTRLSETKEY,", "\"secret\", (sizet)6);", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMINFO,", "\"label\", (sizet)5);", "*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMSALT,", "\"salt\", (sizet)4);", "*p++ = OSSLPARAMconstructsizet(OSSLKDFPARAMMACSIZE, (sizet)20);", "*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": 5, "subsections": [ { "name": "Auxiliary function", "lines": 2 }, { "name": "H(x) = hash(x, digest=md)", "lines": 6 }, { "name": "Identity", "lines": 3 }, { "name": "Supported parameters", "lines": 15 } ] }, { "name": "NOTES", "lines": 8, "subsections": [] }, { "name": "EXAMPLES", "lines": 84, "subsections": [] }, { "name": "CONFORMING TO", "lines": 2, "subsections": [] }, { "name": "SEE ALSO", "lines": 3, "subsections": [] }, { "name": "HISTORY", "lines": 2, "subsections": [] }, { "name": "COPYRIGHT", "lines": 10, "subsections": [] } ], "sections": { "NAME": { "content": "EVPKDF-SS - The Single Step / One Step EVPKDF implementation\n", "subsections": [] }, "DESCRIPTION": { "content": "The EVPKDF-SS algorithm implements the Single Step key derivation function (SSKDF). SSKDF\nderives a key using input such as a shared secret key (that was generated during the\nexecution of a key establishment scheme) and fixedinfo. SSKDF is also informally referred to\nas 'Concat KDF'.\n", "subsections": [ { "name": "Auxiliary function", "content": "The implementation uses a selectable auxiliary function H, which can be one of:\n" }, { "name": "H(x) = hash(x, digest=md)", "content": "H(x) = HMAChash(x, key=salt, digest=md)\nH(x) = KMACxxx(x, key=salt, custom=\"KDF\", outlen=macsize)\n\nBoth the HMAC and KMAC implementations set the key using the 'salt' value. The hash and HMAC\nalso require the digest to be set.\n" }, { "name": "Identity", "content": "\"SSKDF\" is the name for this implementation; it can be used with the EVPKDFfetch()\nfunction.\n" }, { "name": "Supported parameters", "content": "The supported parameters are:\n\n\"properties\" (OSSLKDFPARAMPROPERTIES) \n\"digest\" (OSSLKDFPARAMDIGEST) \n\"mac\" (OSSLKDFPARAMMAC) \n\"maclen\" (OSSLKDFPARAMMACSIZE) \n\"salt\" (OSSLKDFPARAMSALT) \nThese parameters work as described in \"PARAMETERS\" in EVPKDF(3).\n\n\"key\" (EVPKDFCTRLSETKEY) \nThis parameter set the shared secret that is used for key derivation.\n\n\"info\" (OSSLKDFPARAMINFO) \nThis parameter sets an optional value for fixedinfo, also known as otherinfo.\n" } ] }, "NOTES": { "content": "A context for SSKDF can be obtained by calling:\n\nEVPKDF *kdf = EVPKDFfetch(NULL, \"SSKDF\", NULL);\nEVPKDFCTX *kctx = EVPKDFCTXnew(kdf);\n\nThe output length of an SSKDF is specified via the keylen parameter to the EVPKDFderive(3)\nfunction.\n", "subsections": [] }, "EXAMPLES": { "content": "This example derives 10 bytes using H(x) = SHA-256, with the secret key \"secret\" and\nfixedinfo value \"label\":\n\nEVPKDF *kdf;\nEVPKDFCTX *kctx;\nunsigned char out[10];\nOSSLPARAM params[4], *p = params;\n\nkdf = EVPKDFfetch(NULL, \"SSKDF\", NULL);\nkctx = EVPKDFCTXnew(kdf);\nEVPKDFfree(kdf);\n\n*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST,\nSNsha256, strlen(SNsha256));\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMKEY,\n\"secret\", (sizet)6);\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMINFO,\n\"label\", (sizet)5);\n*p = OSSLPARAMconstructend();\nif (EVPKDFderive(kctx, out, sizeof(out), params) <= 0) {\nerror(\"EVPKDFderive\");\n}\n\nEVPKDFCTXfree(kctx);\n\nThis example derives 10 bytes using H(x) = HMAC(SHA-256), with the secret key \"secret\",\nfixedinfo value \"label\" and salt \"salt\":\n\nEVPKDF *kdf;\nEVPKDFCTX *kctx;\nunsigned char out[10];\nOSSLPARAM params[6], *p = params;\n\nkdf = EVPKDFfetch(NULL, \"SSKDF\", NULL);\nkctx = EVPKDFCTXnew(kdf);\nEVPKDFfree(kdf);\n\n*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMMAC,\nSNhmac, strlen(SNhmac));\n*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST,\nSNsha256, strlen(SNsha256));\n*p++ = OSSLPARAMconstructoctetstring(EVPKDFCTRLSETKEY,\n\"secret\", (sizet)6);\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMINFO,\n\"label\", (sizet)5);\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMSALT,\n\"salt\", (sizet)4);\n*p = OSSLPARAMconstructend();\nif (EVPKDFderive(kctx, out, sizeof(out), params) <= 0) {\nerror(\"EVPKDFderive\");\n}\n\nEVPKDFCTXfree(kctx);\n\nThis example derives 10 bytes using H(x) = KMAC128(x,salt,outlen), with the secret key\n\"secret\" fixedinfo value \"label\", salt of \"salt\" and KMAC outlen of 20:\n\nEVPKDF *kdf;\nEVPKDFCTX *kctx;\nunsigned char out[10];\nOSSLPARAM params[7], *p = params;\n\nkdf = EVPKDFfetch(NULL, \"SSKDF\", NULL);\nkctx = EVPKDFCTXnew(kdf);\nEVPKDFfree(kdf);\n\n*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMMAC,\nSNkmac128, strlen(SNkmac128));\n*p++ = OSSLPARAMconstructutf8string(OSSLKDFPARAMDIGEST,\nSNsha256, strlen(SNsha256));\n*p++ = OSSLPARAMconstructoctetstring(EVPKDFCTRLSETKEY,\n\"secret\", (sizet)6);\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMINFO,\n\"label\", (sizet)5);\n*p++ = OSSLPARAMconstructoctetstring(OSSLKDFPARAMSALT,\n\"salt\", (sizet)4);\n*p++ = OSSLPARAMconstructsizet(OSSLKDFPARAMMACSIZE, (sizet)20);\n*p = OSSLPARAMconstructend();\nif (EVPKDFderive(kctx, out, sizeof(out), params) <= 0) {\nerror(\"EVPKDFderive\");\n}\n\nEVPKDFCTXfree(kctx);\n", "subsections": [] }, "CONFORMING TO": { "content": "NIST SP800-56Cr1.\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. Copyright (c) 2019,\nOracle and/or its affiliates. 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-SS(7SSL)", "subsections": [] } } } }