gistfile1.txt

/**
 * Given a secKeyRef, puts it into the keychain to extract its data for easier comparison
 */
+ (NSData *)transformPublicKeyToData:(SecKeyRef)key
{
    NSString *const keychainTag = @"X509_KEY";
    NSData *publicKeyData;
    OSStatus putResult, delResult = noErr;

    // Params for putting the key first
    NSMutableDictionary *putKeyParams = [NSMutableDictionary new];
    putKeyParams[(__bridge id) kSecClass] = (__bridge id) kSecClassKey;
    putKeyParams[(__bridge id) kSecAttrApplicationTag] = keychainTag;
    putKeyParams[(__bridge id) kSecValueRef] = (__bridge id) (key);
    putKeyParams[(__bridge id) kSecReturnData] = (__bridge id) (kCFBooleanTrue); // Request the key's data to be returned too

    // Params for deleting the data
    NSMutableDictionary *delKeyParams = [[NSMutableDictionary alloc] init];
    delKeyParams[(__bridge id) kSecClass] = (__bridge id) kSecClassKey;
    delKeyParams[(__bridge id) kSecAttrApplicationTag] = keychainTag;
    delKeyParams[(__bridge id) kSecReturnData] = (__bridge id) (kCFBooleanTrue);

    // Put the key
    putResult = SecItemAdd((__bridge CFDictionaryRef) putKeyParams, (void *)&publicKeyData);
    // Delete the key
    delResult = SecItemDelete((__bridge CFDictionaryRef)(delKeyParams));

    if ((putResult != errSecSuccess) || (delResult != errSecSuccess))
    {
        publicKeyData = nil;
    }

    return publicKeyData;
}

Is reverse form possible? I want to get SecKeyRef from NSData for private key. I tried similar approach and it work for public key but not for private key. Is it possible for private key as well?