Generate key pair on iphone and print to log as NSString
iphone, keychain, security
Solution
You can use SecItemCopyMatching to get key's NSData. Check `getPublicKeyBits` method in Apple's CryptoExercise, it implements exactly what you need.
Then you can convert `NSData` to a string. Perhaps, `Base64` encoding will suite your needs. Here you can find `Base64` encoding/decoding sample for iPhone. Alternatively, this answer may also be useful for `Base64` encoding.
Problem
Following Apple example code in: http://developer.apple.com/library/ios/#documentation/Security/Conceptual/CertKeyTrustProgGuide/iPhone_Tasks/iPhone_Tasks.html I'm able to successfully generate key-pair with the code snippet below, but unable to print the keys... The function SecKeyGeneratePair() - returns the keys as SecKeyRef type. I have no idea how to handle this type, I understand that this is the keychain representation but how can I actually view the key-pair as NSString?? More specifically, how to convert SecKeyRef to NSString?? ``` static const UInt8 publicKeyIdentifier[] = "com.apple.sample.publickey\0"; static const UInt8 privateKeyIdentifier[] = "com.apple.sample.privatekey\0"; // 1 - (void)generateKeyPairPlease { OSStatus status = noErr; NSMutableDictionary *privateKeyAttr = [[NSMutableDictionary alloc] init]; NSMutableDictionary *publicKeyAttr = [[NSMutableDictionary alloc] init]; NSMutableDictionary *keyPairAttr = [[NSMutableDictionary alloc] init]; // 2 NSData * publicTag = [NSData dataWithBytes:publicKeyIdentifier length:strlen((const char *)publicKeyIdentifier)]; NSData * privateTag = [NSData dataWithBytes:privateKeyIdentifier length:strlen((const char *)privateKeyIdentifier)]; // 3 SecKeyRef publicKey = NULL; SecKeyRef privateKey = NULL; // 4 [keyPairAttr setObject:(id)kSecAttrKeyTypeRSA forKey:(id)kSecAttrKeyType]; // 5 [keyPairAttr setObject:[NSNumber numberWithInt:1024] forKey:(id)kSecAttrKeySizeInBits]; // 6 [privateKeyAttr setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecAttrIsPermanent]; // 7 [privateKeyAttr setObject:privateTag forKey:(id)kSecAttrApplicationTag]; // 8 [publicKeyAttr setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecAttrIsPermanent]; // 9 [publicKeyAttr setObject:publicTag forKey:(id)kSecAttrApplicationTag]; // 10 [keyPairAttr setObject:privateKeyAttr forKey:(id)kSecPrivateKeyAttrs]; // 11 [keyPairAttr setObject:publicKeyAttr forKey:(id)kSecPublicKeyAttrs]; // 12 status = SecKeyGeneratePair((CFDictionaryRef)keyPairAttr, &publicKey, &privateKey); // 13 // error handling... if(privateKeyAttr) [privateKeyAttr release]; if(publicKeyAttr) [publicKeyAttr release]; if(keyPairAttr) [keyPairAttr release]; if(publicKey) CFRelease(publicKey); if(privateKey) CFRelease(privateKey); // 14 } ```