(C) ClickBank Decrypt Instant Notification

Demonstrates how to decrypt a ClickBank instant notification. See Instant Notification Service for more information and alternative code snippets.

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#include <C_CkJsonObject.h>
#include <C_CkBinData.h>
#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    const char *secretKey;
    const char *jsonStr;
    HCkJsonObject json;
    BOOL success;
    HCkBinData bdNotif;
    HCkBinData bdIv;
    HCkCrypt2 crypt;
    const char *hexSha1;
    HCkBinData bdKey;

    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // secret key from your ClickBank account
    secretKey = "MY_SECRET_KEY";

    jsonStr = "{\"notification\":\"BASE64_NOTIFICATION\",\"iv\":\"BASE64_IV\"}";

    json = CkJsonObject_Create();
    success = CkJsonObject_Load(json,jsonStr);

    // Get the encrypted notification (binary) and IV from the JSON.
    bdNotif = CkBinData_Create();
    bdIv = CkBinData_Create();

    success = CkBinData_AppendEncoded(bdNotif,CkJsonObject_stringOf(json,"notification"),"base64");
    success = CkBinData_AppendEncoded(bdIv,CkJsonObject_stringOf(json,"iv"),"base64");

    // Get an SHA1 digest (as a hex string) of the secret key.
    // A SHA1 digest is 20 bytes.  Therefore the hex string is 40 chars.
    // Treat each us-ascii char as a binary byte of the secret key.
    // 256-bit AES needs a 256-bit key, which is 32-bytes.  Therefore
    // use the 1st 32 us-ascii chars of the hex SHA1 as the AES secret key.

    crypt = CkCrypt2_Create();
    // Because we're using the hex string as the actual AES key, it matters whether the hex is uppercase or lowercase.
    // We want lowercase.
    CkCrypt2_putEncodingMode(crypt,"hex_lower");
    CkCrypt2_putHashAlgorithm(crypt,"sha1");
    hexSha1 = CkCrypt2_hashStringENC(crypt,secretKey);
    printf("%s\n",hexSha1);

    // Treat the hex string as binary data for the AES key..
    bdKey = CkBinData_Create();
    CkBinData_AppendString(bdKey,hexSha1,"us-ascii");
    CkBinData_RemoveChunk(bdKey,32,8);

    CkCrypt2_putKeyLength(crypt,256);
    CkCrypt2_putCryptAlgorithm(crypt,"aes");
    CkCrypt2_putCipherMode(crypt,"cbc");

    // We can use any encoding because were just getting the binary bytes in an encoding, and then setting from the same encoding.
    // We'll just use base64..
    CkCrypt2_SetEncodedIV(crypt,CkBinData_getEncoded(bdIv,"base64"),"base64");
    CkCrypt2_SetEncodedKey(crypt,CkBinData_getEncoded(bdKey,"base64"),"base64");

    CkCrypt2_DecryptBd(crypt,bdNotif);
    printf("Decrypted: %s\n",CkBinData_getString(bdNotif,"utf-8"));


    CkJsonObject_Dispose(json);
    CkBinData_Dispose(bdNotif);
    CkBinData_Dispose(bdIv);
    CkCrypt2_Dispose(crypt);
    CkBinData_Dispose(bdKey);

    }