(Objective-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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#import <NSString.h>
#import <CkoJsonObject.h>
#import <CkoBinData.h>
#import <CkoCrypt2.h>

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

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

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

CkoJsonObject *json = [[CkoJsonObject alloc] init];
BOOL success = [json Load: jsonStr];

// Get the encrypted notification (binary) and IV from the JSON.
CkoBinData *bdNotif = [[CkoBinData alloc] init];
CkoBinData *bdIv = [[CkoBinData alloc] init];

success = [bdNotif AppendEncoded: [json StringOf: @"notification"] encoding: @"base64"];
success = [bdIv AppendEncoded: [json StringOf: @"iv"] encoding: @"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.

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];
// Because we're using the hex string as the actual AES key, it matters whether the hex is uppercase or lowercase.
// We want lowercase.
crypt.EncodingMode = @"hex_lower";
crypt.HashAlgorithm = @"sha1";
NSString *hexSha1 = [crypt HashStringENC: secretKey];
NSLog(@"%@",hexSha1);

// Treat the hex string as binary data for the AES key..
CkoBinData *bdKey = [[CkoBinData alloc] init];
[bdKey AppendString: hexSha1 charset: @"us-ascii"];
[bdKey RemoveChunk: [NSNumber numberWithInt: 32] numBytes: [NSNumber numberWithInt: 8]];

crypt.KeyLength = [NSNumber numberWithInt:256];
crypt.CryptAlgorithm = @"aes";
crypt.CipherMode = @"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..
[crypt SetEncodedIV: [bdIv GetEncoded: @"base64"] encoding: @"base64"];
[crypt SetEncodedKey: [bdKey GetEncoded: @"base64"] encoding: @"base64"];

[crypt DecryptBd: bdNotif];
NSLog(@"%@%@",@"Decrypted: ",[bdNotif GetString: @"utf-8"]);