How to hash plaintext.

sha256.m

#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonDigest.h>


NSString* const MDXHashSalt = @"usesomekindofsecret";


@interface MDXHash : NSObject
- (NSString *)createHash:(NSString *)plaintext;
@end

@implementation MDXHash

- (NSString *)createHash:(NSString *)plaintext
{
    // Combine password with salt.
    NSMutableData* buffer = [NSMutableData dataWithData:[plaintext dataUsingEncoding:NSUTF8StringEncoding]];
    [buffer appendData:[MDXHashSalt dataUsingEncoding:NSUTF8StringEncoding]];
    
    NSData* digest = [self createHashFromData:buffer];
    
    // Adapted from: https://ademcan.net/blog/2018/08/03/how-to-convert-a-nsdata-hexstring-to-a-nsstring-in-objective-c/
    NSMutableString* sb = [[NSMutableString alloc] initWithCapacity:([digest length] * 2)];
    
    const unsigned char* bytes = (const unsigned char *)[digest bytes];
    
    for (int i = 0; i < [digest length]; i++) {
        [sb appendFormat:@"%02lx", (unsigned long)bytes[i]];
    }
    
    return [NSString stringWithString:sb];
}

- (NSData *)createHashFromData:(NSData *)data
{
    // Adapted from: https://stackoverflow.com/a/6228385/155167
    unsigned char hash[CC_SHA256_DIGEST_LENGTH];
    
    if (CC_SHA256([data bytes], (CC_LONG)[data length], hash)) {
        NSData* sha = [NSData dataWithBytes:hash length:CC_SHA256_DIGEST_LENGTH];
        return sha;
    }
    
    // We don't want to return nil.
    return [[NSData alloc] init];
}

@end


int main(int argc, char *argv[]) {
    @autoreleasepool {
        id hasher = [[MDXHash alloc] init];
        NSString* result = [hasher createHash:@"Hello, World!"];
        NSLog(@"%@", result);
    }
}