Generate SHA256 hash in Objective-C

Objective-C method whose output matches output from random site online

-(NSString*)sha256HashForText:(NSString*)text {
    const char* utf8chars = [text UTF8String];
    unsigned char result[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256(utf8chars, (CC_LONG)strlen(utf8chars), result);

    NSMutableString *ret = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH*2];
    for(int i = 0; i<CC_SHA256_DIGEST_LENGTH; i++) {
        [ret appendFormat:@"%02x",result[i]];
    }
    return ret;
}

Taken from this Gist.

#import <CommonCrypto/CommonDigest.h>

Objective-C: SHA256 is only two lines:

+ (NSData *)doSha256:(NSData *)dataIn {
    NSMutableData *macOut = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
    CC_SHA256(dataIn.bytes, dataIn.length, macOut.mutableBytes);
    return macOut;
}

Swift 3

func sha256Hex(string: String) -> String? {
    guard let messageData = string.data(using:String.Encoding.utf8) else { return nil }
    var digestData = Data(count: Int(CC_SHA256_DIGEST_LENGTH))

    _ = digestData.withUnsafeMutableBytes {digestBytes in
        messageData.withUnsafeBytes {messageBytes in
            CC_SHA256(messageBytes, CC_LONG(messageData.count), digestBytes)
        }
    }

    return digestData.map { String(format: "%02hhx", $0) }.joined()
}

// Test

let sha256HexString = sha256Hex(string:"Hello")
print("sha256HexString: \(sha256HexString!)")

sha256HexString: "185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969"

You need to include the appropriate header file:

#include <CommonCrypto/CommonDigest.h>

According to the Cryptographic Services documentation this should be available on both iOS and OS X.

In OS X v10.5 and later and iOS 5.0 and later, Common Crypto provides low-level C support for encryption and decryption. Common Crypto is not as straightforward as Security Transforms, but provides a wider range of features, including additional hashing schemes, cipher modes, and so on.