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(Unicode C) Decrypt 256-bit AES GCM Produced by Something UnknownDemonstrates how to decrypt something produced elsewhere (unknown) with 256-bit AES GCM.
#include <C_CkCrypt2W.h> #include <C_CkBinDataW.h> void ChilkatSample(void) { const wchar_t *keyBase64; const wchar_t *ivBase64Url; const wchar_t *cipherBase64Url; HCkCrypt2W crypt; BOOL success; HCkBinDataW bdEncrypted; HCkBinDataW bdAuthTag; int numBytes; const wchar_t *authTagHex; const wchar_t *originalText; // This example assumes the Chilkat API to have been previously unlocked. // See Global Unlock Sample for sample code. // We have the following to decrypt: // Key (Base64): keyBase64 = L"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; // IV (Base64Url): ivBase64Url = L"xrvaINMLqotAbWRK"; // ciphertext (base64url): cipherBase64Url = L"RtGNAS-zQOxSB8W0HfqJjCoyt9KgImW_l-HjVC40hOOl-RNfRF3hzDIT1kvFVF8i_KX9XmqAftb6lyq-jLCEc_MSgqt3q1ixv3Ez4SbS3G5e3qGzLwxIMi2sCt00aDNwK2ipsJ4aw8s7ePPnl4oY-y1st9rwCWR0rrgEZwS9jmS4uJWGPn9K3jbKRnMslznDbtFLNJctMVXBTP-cv47JelxLCBOQSlK29rMuEFrhHR_VQrPq6gtZaBVSXZSYT0XOklp7nu9mVhrMCRtBCC5oiu5MPE5JYx4ANo3hUY7_NyQl2bpn9GfRXrdvqRGE-gy2upj-cDkm0t_tV8xmYge9DBQTH3B_4BGl2qTk_o-m7pEmKkS8XSdQhGcuFlykqrkE8SzB5I8esfzWOM0pwxbz0H_VaylKYHY="; crypt = CkCrypt2W_Create(); CkCrypt2W_putCryptAlgorithm(crypt,L"aes"); CkCrypt2W_putCipherMode(crypt,L"gcm"); CkCrypt2W_putKeyLength(crypt,256); success = CkCrypt2W_SetEncodedAad(crypt,L"random",L"ascii"); CkCrypt2W_SetEncodedKey(crypt,keyBase64,L"base64"); CkCrypt2W_SetEncodedIV(crypt,ivBase64Url,L"base64url"); // The cipher text contains the 16-byte auth tag at the end. // get it separately.. bdEncrypted = CkBinDataW_Create(); bdAuthTag = CkBinDataW_Create(); success = CkBinDataW_AppendEncoded(bdEncrypted,cipherBase64Url,L"base64url"); numBytes = CkBinDataW_getNumBytes(bdEncrypted); authTagHex = CkBinDataW_getEncodedChunk(bdEncrypted,numBytes - 16,16,L"hex"); wprintf(L"Auth tag in hex: %s\n",authTagHex); success = CkBinDataW_AppendEncoded(bdAuthTag,authTagHex,L"hex"); CkBinDataW_RemoveChunk(bdEncrypted,numBytes - 16,16); // Use this special value to tell Chilkat to ignore the auth tag. success = CkCrypt2W_SetEncodedAuthTag(crypt,L"FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",L"hex"); // Decrypt CkCrypt2W_putEncodingMode(crypt,L"base64"); originalText = CkCrypt2W_decryptStringENC(crypt,CkBinDataW_getEncoded(bdEncrypted,L"base64")); if (CkCrypt2W_getLastMethodSuccess(crypt) == FALSE) { wprintf(L"%s\n",CkCrypt2W_lastErrorText(crypt)); } else { wprintf(L"%s\n",originalText); wprintf(L"Success.\n"); } // Decrypted text CkCrypt2W_Dispose(crypt); CkBinDataW_Dispose(bdEncrypted); CkBinDataW_Dispose(bdAuthTag); } |
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