[Swift._NSContiguousString bytes]: unrecognized selector sent to instance - swift

Question

I'm working on Xcode version 7.1 (7B91b), I'm using Swift and building an OSX application (10.11.2). I'm trying to generate and store RSA key pairs to be used for data encryption / decryption. Here's the implementation that has been taken from: 'AsymmetricCrypto Github
// Constants
private let kAsymmetricCryptoManagerApplicationTag = "com.AsymmetricCrypto.keypair"
private let kAsymmetricCryptoManagerKeyType = kSecAttrKeyTypeRSA
private let kAsymmetricCryptoManagerKeySize = 2048
private let kAsymmetricCryptoManagerCypheredBufferSize = 1024
private let kAsymmetricCryptoManagerSecPadding: SecPadding = .PKCS1
func createSecureKeyPair(completion: ((success: Bool, error: AsymmetricCryptoException?) -> Void)? = nil) {
// private key parameters
let privateKeyParams: [String: AnyObject] = [
kSecAttrIsPermanent as String: false,
kSecAttrApplicationTag as String: kAsymmetricCryptoManagerApplicationTag
]
// private key parameters
let publicKeyParams: [String: AnyObject] = [
kSecAttrIsPermanent as String: false,
kSecAttrApplicationTag as String: kAsymmetricCryptoManagerApplicationTag
]
// global parameters for our key generation
let parameters: [String: AnyObject] = [
kSecAttrKeyType as String: kAsymmetricCryptoManagerKeyType,
kSecAttrKeySizeInBits as String: kAsymmetricCryptoManagerKeySize,
kSecPublicKeyAttrs as String: publicKeyParams,
kSecPrivateKeyAttrs as String: privateKeyParams,
]
// asynchronously generate the key pair and call the completion block
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) { () -> Void in
var pubKey, privKey: SecKeyRef?
let status = SecKeyGeneratePair(parameters, &pubKey, &privKey)
if status == errSecSuccess {
dispatch_async(dispatch_get_main_queue(), { completion?(success: true, error: nil) })
} else {
var error = AsymmetricCryptoException.UnknownError
switch (status) {
case errSecDuplicateItem: error = .DuplicateFoundWhileTryingToCreateKey
case errSecItemNotFound: error = .KeyNotFound
case errSecAuthFailed: error = .AuthFailed
default: break
}
dispatch_async(dispatch_get_main_queue(), { completion?(success: false, error: error) })
}
}
}
Upon calling the createSecureKeyPair(), as follows:
AsymmetricCryptoManager.sharedInstance.createSecureKeyPair({
(success, error) -> Void in
if (success) {
print("keys created")
} else {
print("error: \(error)")
}
})
I get this error:
2015-12-26 03:55:46.113 sectest[17165:20928431] -[Swift._NSContiguousString bytes]: unrecognized selector sent to instance 0x610000045880
and of course, the exception AsymmetricCryptoException.UnknownError is returned (meaning that the error is of an unknown nature), plus if it helps, SecKeyGeneratePair() returns the value -2070
The weird part is that the keys (public and private) are actually created in the Keychain as such:
What is this error and how can get the expected behavior out of the code above?

Answer 1

I got the answer to the problem from the Apple Developer Forums. The problem is with:
private let kAsymmetricCryptoManagerApplicationTag = "com.AsymmetricCrypto.keypair"
The values for key kSecAttrApplicationTag of params dictionaries need to be a CFDataRef, not String. The below line, resolves the problem.
private let kAsymmetricCryptoManagerApplicationTag = "com.sectest.keypair".dataUsingEncoding(NSUTF8StringEncoding)!