Brilliant little piece of code to help you base64 encode NSStrings in iOS / objective-c using native libraries. Thanks to the original author, Arthur Sabintsev; find his blog here: http://blog.artsabintsev.com/native-base64-encoding-in-ios-pt-1

Native Base64 String Encoding

// Pre-iOS 7
+ (NSString *)base64EncodeString:(NSString *)stringToEncode
{
    CFHTTPMessageRef messageRef = CFHTTPMessageCreateEmpty(kCFAllocatorDefault, FALSE);
    CFHTTPMessageAddAuthentication(messageRef, NULL, CFSTR("AS"), (__bridge CFStringRef)stringToEncode, kCFHTTPAuthenticationSchemeBasic, FALSE);

    CFStringRef authStringRef = CFHTTPMessageCopyHeaderFieldValue(messageRef, CFSTR("Authorization"));
    NSString *encodedString = [(__bridge NSString *)authStringRef substringFromIndex:10];

    CFRelease(messageRef);
    CFRelease(authStringRef);

    return encodedString;
}


// For iOS 7
+ (instancetype)encodeBase64String:(NSString *)stringToEncode
{
    NSData *dataToEncode = [stringToEncode dataUsingEncoding:NSUTF8StringEncoding];
    NSData *encodedData = [dataToEncode base64EncodedDataWithOptions:0];
    NSString *encodedString = [[NSString alloc] initWithData:encodedData encoding:NSUTF8StringEncoding];
    
    return encodedString;
}

+ (instancetype)decodeBase64String:(NSString *)stringToDeccode
{
    NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:stringToDeccode options:0];
    NSString *decodedString = [[NSString alloc] initWithData:decodedData encoding:NSUTF8StringEncoding];
    
    return decodedString;
}