PBKDF2 using CommonCrypto on iOS

Question

I'm trying to use CommonCrypto to generate keys using PBKDF2 but I can't seem to import CommonCrypto/CommonKeyDerivation.h, I just errors that it is not found.

Any ideas?

edit: I should probably mention I have already added the security framework and I can import all of the other CommonCrypto headers.

Answer 1

Here's how i generate AES256 keys. The only interesting this is that i get CommonCrypto to estimate for me how many rounds to use. It seems pretty straightforwards.

#import <CommonCrypto/CommonKeyDerivation.h>

...

// Makes a random 256-bit salt
- (NSData*)generateSalt256 {
    unsigned char salt[32];
    for (int i=0; i<32; i++) {
        salt[i] = (unsigned char)arc4random();
    }
    return [NSData dataWithBytes:salt length:32];
}

...

// Make keys!
NSString* myPass = @"MyPassword1234";
NSData* myPassData = [myPass dataUsingEncoding:NSUTF8StringEncoding];
NSData* salt = [self generateSalt256];

// How many rounds to use so that it takes 0.1s ?
int rounds = CCCalibratePBKDF(kCCPBKDF2, myPassData.length, salt.length, kCCPRFHmacAlgSHA256, 32, 100);

// Open CommonKeyDerivation.h for help
unsigned char key[32];
CCKeyDerivationPBKDF(kCCPBKDF2, myPassData.bytes, myPassData.length, salt.bytes, salt.length, kCCPRFHmacAlgSHA256, rounds, key, 32);

Answer 2

1. Add this library to your project libcommonCrypto.dylib
2. #import into hash key generation class.
3. use following code to generate hash key.

This is the code what i have used:

// Salt data getting from salt string.
NSData *saltData = [@"Salt String" dataUsingEncoding:NSUTF8StringEncoding];

// Data of String to generate Hash key(hexa decimal string).
NSData *passwordData = [@"Hash key generated string" dataUsingEncoding:NSUTF8StringEncoding];

// Hash key (hexa decimal) string data length.
NSMutableData *hashKeyData = [NSMutableData dataWithLength:CC_SHA1_DIGEST_LENGTH];

// Key Derivation using PBKDF2 algorithm.
int result = CCKeyDerivationPBKDF(kCCPBKDF2, passwordData.bytes, passwordData.length, saltData.bytes, saltData.length, kCCPRFHmacAlgSHA1, 1000, hashKeyData.mutableBytes, hashKeyData.length);

// Hexa decimal or hash key string from hash key data.
NSString *hexDecimalString = hashKeyData.description;

NSLog(@"Hexa decimal string:%@", hexDecimalString);

Answer 3

Are you building for iOS5 ? or earlier versions ?

Both API, CCKeyDerivationPBKDF and CCCalibratePBKDF, defined in the header file are only available on IOS5 (or OSX 10.7) and later.

You can make sure the file exists by executing this inside a terminal window:

$ find /Developer/ -name CommonKeyDerivation.h
/Developer//Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.0.sdk/usr/include/CommonCrypto/CommonKeyDerivation.h
/Developer//Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator5.0.sdk/usr/include/CommonCrypto/CommonKeyDerivation.h
/Developer//SDKs/MacOSX10.7.sdk/usr/include/CommonCrypto/CommonKeyDerivation.h