Encrypt an NSString

Question

I'd like to encrypt an NSString so that it isn't human-readable. The level of security doesnt manner (in other words, if somebody were to decrypt the text there wouldn't be any sensitive information for them to steal.

NSString *myTextToEncrypt = @"Hello World!";

[myTextToEncrypt encrypt];

// myTextToEncrypt is now something unreadable, like '2rwzdn1405'

Then I should be able to unencrypt this string

[myTextToEncrypt unencrypt]; // myTextToEncrypt should now be @"Hello World!" again

How do I do this? I've read some about CommonCrypto and AES Encryption but this all seems like overkill for what I'm trying to do (the encryption methods I've read are all for passwords or other sensitive pieces of data)

Inder Kumar Rathore · Answer 1 · 2013-08-11T05:18:51.563

Simplest one is use your own encryption, e.g.

Utils.h

@interface Utils : NSObject
+(NSString*)encyptString:(NSString*)str;
+(NSString*)decryptString:(NSString*)str;
@end

Utils.m

#import "Utils.h"

int offset = 15;
@implementation Utils
+(NSString*)encyptString:(NSString*)str
{
    NSMutableString *encrptedString = [[NSMutableString alloc] init];
    for (int i = 0; i < str.length; i++) {
        unichar character = [str characterAtIndex:i];
        character += offset;
        [encrptedString appendFormat:@"%C",character];
    }
    return encrptedString;
}

+(NSString*)decryptString:(NSString*)str
{
    NSMutableString *decrptedString = [[NSMutableString alloc] init];
    for (int i = 0; i < str.length; i++) {
        unichar character = [str characterAtIndex:i];
        character -= offset;
        [decrptedString appendFormat:@"%C",character];
    }
    return decrptedString;
}
@end

How to use it

NSString *str = @"hello world";
NSString *enr = [Utils encyptString:str];
NSLog(@"Encrypted Text=%@", enr);
NSLog(@"Decrypted Text=%@", [Utils decryptString:enr]);

Logs

2013-08-11 10:44:09.409 DeviceTest[445:c07] Encrypted Text=wt{{~/~{s
2013-08-11 10:44:09.412 DeviceTest[445:c07] Decrypted Text=hello world

This is not encryption, this is encoding, which is easier to penetrate. — M. Ryan, Nov 25 '13 at 20:30
@Jasconius How much easier is it to penetrate? I thinking of using encoding to 'encrypt' some text messages. — Supertecnoboff, Jul 31 '14 at 11:21
@InderKumarRathore The offset needs to have a limit? or can I pass the number I want no matter what the text is? — Alejandro Cotilla, Dec 20 '14 at 15:05

score 2 · Accepted Answer · answered Aug 11 '13 at 05:02

2

You can use base64 to do this.

There are some implementations in Objective-C available (as this one).

Note that the content will be about 30% bigger after it's encoded.

answered Aug 11 '13 at 05:02

Marcelo

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Encrypt an NSString

2 Answers2