Generate SHA256 hash in Objective-C

Question

So I need to generate a Sha256 password in Objective-C, and can't figure out for the life of me how to do it! Is there something easy I'm just missing?

I've tried implementing the following method (which was written for iPhone, but I figured maybe it'd work cross-platform, as some Objective-C code does)

-(NSString*)sha256HashFor:(NSString*)input
{
    const char* str = [input UTF8String];
    unsigned char result[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256(str, strlen(str), 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;
}

But that just spat out errors about CC_SHA256_DIGEST_LENGTH being an undeclared identifier.

James Holderness · Accepted Answer · 2013-05-31T21:33:23.633

24

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.

edited May 31 '13 at 21:33

answered May 31 '13 at 21:26

James Holderness

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2

I would recommend using #import instead of #include as it ensures the header is only included once. #import prevent recursive inclusion. – d00dle May 31 '13 at 22:39
2

@doodle It's a C header file though - it already has that checking built in. – James Holderness May 31 '13 at 22:51
While that did work, it for some reason isn't producing the same sha256 as my PHP script. – garetmckinley May 31 '13 at 23:00
I'm sha256 encrypting the password along with Zo4rU5Z1YyKJAASY0PT6EUg7BBYdlEhPaNLuxAwU8lqu1ElzHv0Ri7EM6irpx5w appended on the end, and the values from the php and objective-c side are different. – garetmckinley May 31 '13 at 23:02
Nevermind, I got it fixed. I just had an error in my code. Thanks for the help James! – garetmckinley May 31 '13 at 23:07
Great! I was struggling to think of a reason why it would have been different. :) – James Holderness May 31 '13 at 23:10

zaph · Answer 2 · 2016-12-05T18:20:08.933

11

#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"

edited Dec 05 '16 at 18:20

answered Sep 11 '14 at 00:09

zaph

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i am trying to convert it to nsstring in order to save it to database but its not working. Could you please tell me know to store the SHA256 key to database: NSString* newStr = [[NSString alloc] initWithData:sha256 encoding:NSUTF8StringEncoding]; – Vikas Bansal Oct 14 '15 at 06:13
1

It is not possible to convert arbitrary data into a string, not all 8-bit bytes map to character encodings. There are two common options: hexadecimal or Base64 representations.There may also be the option of putting the raw data into the database. – zaph Oct 14 '15 at 10:52
now, I am doing it like this.. Is this correct? NSString * str = [sha256Data base64EncodedStringWithOptions:0]; – Vikas Bansal Oct 14 '15 at 11:09

score 6 · Answer 3 · answered Mar 25 '20 at 19:32

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.

score 3 · Answer 4 · answered Oct 13 '19 at 18:22

a modified version of @zaph answer in Objective-C with NSString as input and output:

-(NSString*)sha256HashFor:(NSString*)input
{
    NSData* data = [input dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableData *sha256Data = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
    CC_SHA256([data bytes], (CC_LONG)[data length], [sha256Data mutableBytes]);
    return [sha256Data base64EncodedStringWithOptions:0];
}

score 1 · Answer 5 · answered Sep 10 '14 at 22:32

1

Check out the NSHash cocoa pod. It has a bunch of different hashing methods including SHA256.

https://github.com/jerolimov/NSHash

answered Sep 10 '14 at 22:32

Jeff Ames

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Generate SHA256 hash in Objective-C

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