Common hashing algorithms on top of NSString.

NSString+Hash.h

//
//  NSString+Hash.h
//
//  Created by Maksym Huk on 10/10/12.
//  Copyright (c) 2012 Maksym Huk. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSString (Hash)

- (NSString*)hashSHA1;
- (NSString*)hashMD5;

@end

NSString+Hash.m

//
//  NSString+Hash.m
//
//  Created by Maksym Huk on 10/10/12.
//  Copyright (c) 2012 Maksym Huk. All rights reserved.
//

#import <CommonCrypto/CommonCrypto.h>

#import "NSString+Hash.h"

@implementation NSString (Hash)

- (NSString*)hashSHA1
{
    const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:self.length];
    
    uint8_t digest[CC_SHA1_DIGEST_LENGTH];
    
    CC_SHA1(data.bytes, data.length, digest);
    
    NSMutableString* output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 2];
    
    for(int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x", digest[i]];
    
    return output;
}

- (NSString *)hashMD5
{
    const char *cStr = [self UTF8String];
    unsigned char digest[16];
    CC_MD5( cStr, strlen(cStr), digest ); // This is the md5 call
    
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    
    for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x", digest[i]];
    
    return  output;   
}

@end