Convert NSData to SecKeyRef

Question

I've generated private and public keys with SecKeyGeneratePair and I've converted a SecKeyRef to NSData with

size_t keySize = SecKeyGetBlockSize(publicKey);

NSData *keyData = [NSData dataWithBytes:publicKey length:keySize];

But unluckily I'm unable to re-convert keyData in a SecKeyRef type.

Here's the question: How can I reconvert the NSData in a SecKeyRef type?

This is the code!

    //
    //  RSA.m
    //  example
    //
    //  Created by Ferdinando Picone on 07/11/13.
    //  Copyright (c) 2013 Ferdinando Picone. All rights reserved.
    //

    #import "RSA.h"
    #import <Security/Security.h>
    #import "NSData+Base64.h"

    static const UInt8 publicKeyIdentifier[] = "com.apple.sample.publickey\0";
    static const UInt8 privateKeyIdentifier[] = "com.apple.sample.privatekey\0";
    
    SecKeyRef publicKey = NULL;
    SecKeyRef privateKey = NULL;

    @implementation RSA

    -(void)start{
RSA *one = [[RSA alloc]init];


// Generate public and private key
[one generateKeyPairPlease];
NSLog(@" %@", publicKey);
NSLog(@" %@", privateKey);

//Convert public key in NSData Type
size_t  keySize = SecKeyGetBlockSize(publicKey);
NSData  *keyData = [NSData dataWithBytes:publicKey length:keySize];
NSLog (@" %@", keyData);

//Convert public key in NSString Type
NSString *keyStringB64 =[keyData base64EncodedString];


//Reconvert NSString in a NSData Type (newKeyData)
NSData *newKeyData = [NSData dataFromBase64String:keyStringB64];

NSLog(@" %@", newKeyData);

// In the debug you can see that keyData==newKeyData

// NOW I NEED TO RECONVERT newKeyData in a SecKeyRef newPublicKey
SecKeyRef newPublicKey=NULL;

    }

    -(void) generateKeyPairPlease{

OSStatus status = noErr;
NSMutableDictionary *privateKeyAttr = [[NSMutableDictionary alloc] init];
NSMutableDictionary *publicKeyAttr = [[NSMutableDictionary alloc] init];
NSMutableDictionary *keyPairAttr = [[NSMutableDictionary alloc] init];

NSData * publicTag = [NSData dataWithBytes:publicKeyIdentifier
                                    length:strlen((const char *)publicKeyIdentifier)];
NSData * privateTag = [NSData dataWithBytes:privateKeyIdentifier
                                     length:strlen((const char *)privateKeyIdentifier)];


[keyPairAttr setObject:(__bridge id)kSecAttrKeyTypeRSA
                forKey:(__bridge id)kSecAttrKeyType];
[keyPairAttr setObject:[NSNumber numberWithInt:1024]
                forKey:(__bridge id)kSecAttrKeySizeInBits];

[privateKeyAttr setObject:[NSNumber numberWithBool:YES]
                   forKey:(__bridge id)kSecAttrIsPermanent];
[privateKeyAttr setObject:privateTag
                   forKey:(__bridge id)kSecAttrApplicationTag];

[publicKeyAttr setObject:[NSNumber numberWithBool:YES]
                  forKey:(__bridge id)kSecAttrIsPermanent];
[publicKeyAttr setObject:publicTag
                  forKey:(__bridge id)kSecAttrApplicationTag];

[keyPairAttr setObject:privateKeyAttr
                forKey:(__bridge id)kSecPrivateKeyAttrs];
[keyPairAttr setObject:publicKeyAttr
                forKey:(__bridge id)kSecPublicKeyAttrs];

status = SecKeyGeneratePair((__bridge CFDictionaryRef)keyPairAttr,
                            &publicKey, &privateKey);


    }


    @end

Answer 1

You can create SecKeyRef from NSData using API available in iOS 10.10

- (SecKeyRef)secKeyRefFromFrivateKeyData:(NSData *)privateKeyData
{
    NSDictionary *attributes = @{(__bridge NSString*)kSecAttrKeyType : (__bridge NSString*)kSecAttrKeyTypeRSA,
                                 (__bridge NSString*)kSecAttrKeyClass : (__bridge NSString*)kSecAttrKeyClassPrivate};
    return SecKeyCreateWithData((__bridge CFDataRef)privateKeyData, (__bridge CFDictionaryRef)attributes, NULL);
}