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(Unicode C) ECDSA Sign and VerifyDemonstrates how to create an ECDSA signature on the SHA256 hash of some data, and then verify.
#include <C_CkPrivateKeyW.h> #include <C_CkBinDataW.h> #include <C_CkCrypt2W.h> #include <C_CkEccW.h> #include <C_CkPrngW.h> #include <C_CkAsnW.h> #include <C_CkXmlW.h> #include <C_CkPublicKeyW.h> void ChilkatSample(void) { HCkPrivateKeyW privKey; BOOL success; HCkBinDataW bd; HCkCrypt2W crypt; const wchar_t *hashStr; HCkEccW ecdsa; HCkPrngW prng; const wchar_t *sig; HCkAsnW asn; HCkXmlW xml; const wchar_t *r; const wchar_t *s; HCkPublicKeyW pubKey; HCkEccW ecc2; int result; HCkXmlW xml2; HCkAsnW asn2; const wchar_t *encodedSig; // This example assumes the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. // First load an ECDSA private key to be used for signing. privKey = CkPrivateKeyW_Create(); success = CkPrivateKeyW_LoadEncryptedPemFile(privKey,L"qa_data/ecc/secp256r1-key-pkcs8-secret.pem",L"secret"); if (success == FALSE) { wprintf(L"%s\n",CkPrivateKeyW_lastErrorText(privKey)); CkPrivateKeyW_Dispose(privKey); return; } // Sign the SHA256 hash of some data. bd = CkBinDataW_Create(); success = CkBinDataW_LoadFile(bd,L"qa_data/hamlet.xml"); if (success == FALSE) { wprintf(L"Failed to load file to be hashed.\n"); CkPrivateKeyW_Dispose(privKey); CkBinDataW_Dispose(bd); return; } crypt = CkCrypt2W_Create(); CkCrypt2W_putHashAlgorithm(crypt,L"sha256"); CkCrypt2W_putEncodingMode(crypt,L"base64"); hashStr = CkCrypt2W_hashBdENC(crypt,bd); ecdsa = CkEccW_Create(); prng = CkPrngW_Create(); // Returns ASN.1 signature as a base64 string. sig = CkEccW_signHashENC(ecdsa,hashStr,L"base64",privKey,prng); wprintf(L"sig = %s\n",sig); // The signature is in ASN.1 format (which may be described as the "encoded DSS signature"). // SEQUENCE (2 elem) // INTEGER (255 bit) 4849395540832462044300553275435608522154141569743642905628579547100940... // INTEGER (255 bit) 3680701124244788134409868118208591399799457104230118295614152238560005... // If you wish, you can get the r and s components of the signature like this: asn = CkAsnW_Create(); CkAsnW_LoadEncoded(asn,sig,L"base64"); xml = CkXmlW_Create(); CkXmlW_LoadXml(xml,CkAsnW_asnToXml(asn)); wprintf(L"%s\n",CkXmlW_getXml(xml)); // We now have this: // <?xml version="1.0" encoding="utf-8"?> // <sequence> // <int>6650D422D86BA4A228B5617604E59052591B9B2C32EF324C44D09EF67E5F0060</int> // <int>0CFD9F6AC85042FC70F672C141BA6B2A4CAFBB906C3D907BCCC1BED62B28326F</int> // </sequence> // Get the "r" and "s" as hex strings r = CkXmlW_getChildContentByIndex(xml,0); s = CkXmlW_getChildContentByIndex(xml,1); wprintf(L"r = %s\n",r); wprintf(L"s = %s\n",s); // -------------------------------------------------------------------- // Now verify against the hash of the original data. // Get the corresponding public key. pubKey = CkPublicKeyW_Create(); success = CkPublicKeyW_LoadFromFile(pubKey,L"qa_data/ecc/secp256r1-pub.pem"); if (success == FALSE) { wprintf(L"%s\n",CkPublicKeyW_lastErrorText(pubKey)); CkPrivateKeyW_Dispose(privKey); CkBinDataW_Dispose(bd); CkCrypt2W_Dispose(crypt); CkEccW_Dispose(ecdsa); CkPrngW_Dispose(prng); CkAsnW_Dispose(asn); CkXmlW_Dispose(xml); CkPublicKeyW_Dispose(pubKey); return; } // We already have the SHA256 hash of the original data (hashStr) so no need to re-do it.. ecc2 = CkEccW_Create(); result = CkEccW_VerifyHashENC(ecc2,hashStr,sig,L"base64",pubKey); if (result != 1) { wprintf(L"%s\n",CkEccW_lastErrorText(ecc2)); CkPrivateKeyW_Dispose(privKey); CkBinDataW_Dispose(bd); CkCrypt2W_Dispose(crypt); CkEccW_Dispose(ecdsa); CkPrngW_Dispose(prng); CkAsnW_Dispose(asn); CkXmlW_Dispose(xml); CkPublicKeyW_Dispose(pubKey); CkEccW_Dispose(ecc2); return; } wprintf(L"Verified!\n"); // Note: If we have only r,s and wish to reconstruct the ASN.1 signature, we do it like this: xml2 = CkXmlW_Create(); CkXmlW_putTag(xml2,L"sequence"); CkXmlW_NewChild2(xml2,L"int",r); CkXmlW_NewChild2(xml2,L"int",s); asn2 = CkAsnW_Create(); CkAsnW_LoadAsnXml(asn2,CkXmlW_getXml(xml2)); encodedSig = CkAsnW_getEncodedDer(asn2,L"base64"); wprintf(L"encoded DSS signature: %s\n",encodedSig); // You can go to https://lapo.it/asn1js/ and copy/paste the base64 encodedSig into the online tool, then press the "decode" button. // You will see the ASN.1 such as this: // SEQUENCE (2 elem) // INTEGER (255 bit) 4849395540832462044300553275435608522154141569743642905628579547100940... // INTEGER (255 bit) 3680701124244788134409868118208591399799457104230118295614152238560005... CkPrivateKeyW_Dispose(privKey); CkBinDataW_Dispose(bd); CkCrypt2W_Dispose(crypt); CkEccW_Dispose(ecdsa); CkPrngW_Dispose(prng); CkAsnW_Dispose(asn); CkXmlW_Dispose(xml); CkPublicKeyW_Dispose(pubKey); CkEccW_Dispose(ecc2); CkXmlW_Dispose(xml2); CkAsnW_Dispose(asn2); } |
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