CCCrypt maximum time it returns nil. What is the problem in Encryption - encryption

Question

I trying to write an encryption (AESCBC128) function based on CCCrypt and the CCCrypt is generating a random value.
for example, when I pass 016768821221 to function it'll return "0oTPFcKNWABTpBGgLlzsjw==" for the same iv and Key.
here's the iv: "khabbababab" and the key is : "khabbababab"
why it returns nil. The encryption is correct but some times it returns nil
extension String {
func aesEncrypt(key:String, iv:String, options:Int = kCCOptionPKCS7Padding) -> String? {
if let keyData = key.data(using: String.Encoding.utf8),
let data = self.data(using: String.Encoding.utf8),
let cryptData = NSMutableData(length: Int((data.count)) + kCCBlockSizeAES128) {
let keyLength = kCCKeySizeAES128
let operation: CCOperation = UInt32(kCCEncrypt)
let algoritm: CCAlgorithm = CCOptions(kCCAlgorithmAES128)
let options: CCOptions = UInt32(options)
var numBytesEncrypted :size_t = 0
let cryptStatus = CCCrypt(operation,
algoritm,
CCOptions(options),
(keyData as NSData).bytes, keyLength,
iv,
(data as NSData).bytes, data.count,
cryptData.mutableBytes, cryptData.length,
&numBytesEncrypted)
print(String(data: data, encoding: .utf8) as Any)
if UInt32(cryptStatus) == UInt32(kCCSuccess) {
cryptData.length = Int(numBytesEncrypted)
let base64cryptString = cryptData.base64EncodedString(options: .lineLength64Characters)
print("succccc")
return base64cryptString
}
else {
print("nill nill llllllllll")
return nil
}
}
return nil
}
func aesDecrypt(key:String, iv:String, options:Int = kCCOptionPKCS7Padding) -> String? {
if let keyData = key.data(using: String.Encoding.utf8),
let data = NSData(base64Encoded: self, options: .ignoreUnknownCharacters),
let cryptData = NSMutableData(length: Int((data.length)) + kCCBlockSizeAES128) {
let keyLength = size_t(kCCKeySizeAES128)
let operation: CCOperation = UInt32(kCCDecrypt)
let algoritm: CCAlgorithm = UInt32(kCCAlgorithmAES128)
let options: CCOptions = UInt32(options)
var numBytesEncrypted :size_t = 0
let cryptStatus = CCCrypt(operation,
algoritm,
options,
(keyData as NSData).bytes, keyLength,
iv,
data.bytes, data.length,
cryptData.mutableBytes, cryptData.length,
&numBytesEncrypted)
if UInt32(cryptStatus) == UInt32(kCCSuccess) {
cryptData.length = Int(numBytesEncrypted)
let unencryptedMessage = String(data: cryptData as Data, encoding:String.Encoding.utf8)
return unencryptedMessage
}
else {
return nil
}
}
return nil
}

Answer 1

Your aesEncrypt always passes a keylength of 16 to CCCrypt without checking that the key actually has at least 16 bytes of data.