Saving SecKeyRef device generated public/private key pair on disk

Question

I\'ve generated an RSA symmetric key pair on a device using SecKeyGeneratePair() on a device. I have SecKeyRef struct pointers for each key. So, ho

Answer 1

Ah, found the answer myself; you can get the bytes for a public key using SecItemCopyMatching().

- (NSData *)getPublicKeyBits {
    OSStatus sanityCheck = noErr;
    NSData * publicKeyBits = nil;

    NSMutableDictionary * queryPublicKey = [[NSMutableDictionary alloc] init];

    // Set the public key query dictionary.
    [queryPublicKey setObject:(id)kSecClassKey forKey:(id)kSecClass];
    [queryPublicKey setObject:publicTag forKey:(id)kSecAttrApplicationTag];
    [queryPublicKey setObject:(id)kSecAttrKeyTypeRSA forKey:(id)kSecAttrKeyType];
    [queryPublicKey setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecReturnData];

    // Get the key bits.
    sanityCheck = SecItemCopyMatching((CFDictionaryRef)queryPublicKey, (CFTypeRef *)&publicKeyBits);

    if (sanityCheck != noErr)
    {
        publicKeyBits = nil;
    }

    [queryPublicKey release];

    return publicKeyBits;
}

The above is from Apple's CryptoExercise. Not sure if it works for private keys though.