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

@interface Util : NSObject {}
//	generates a unique id from a string
+ (NSString *)uniqueIDFromString:(NSString *)source;
@end

@implementation Util
//	generates a unique id from a string
+ (NSString *)uniqueIDFromString:(NSString *)source
{
	const char *src = [[source lowercaseString] UTF8String];
	unsigned char result[CC_MD5_DIGEST_LENGTH];
	CC_MD5(src, strlen(src), result);
	
    NSString *ret = [[[NSString alloc] initWithFormat:@"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X", 
                        result[0], result[1], result[2], result[3],
                        result[4], result[5], result[6], result[7],
                        result[8], result[9], result[10], result[11],
                        result[12], result[13], result[14], result[15]
                     ] autorelease];
    
    return ret;
}
@end

This is a simple md5 implementation.

MD5 String Hash

Objective C