Base64

base64.m

static char *alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

@implementation Base64
+ (NSString*)
encode:(NSData*)plainText
{
    int encodedLength = (((([plainText length] % 3) + [plainText length]) / 3) * 4) + 1;
    unsigned char *outputBuffer = malloc(encodedLength);
    unsigned char *inputBuffer = (unsigned char*)[plainText bytes];

    NSInteger i;
    NSInteger j = 0;
    int remain;

    for (i = 0; i < [plainText length]; i += 3) {
        remain = [plainText length] - i;

        outputBuffer[j++] = alphabet[(inputBuffer[i] & 0xFC) >> 2];
        outputBuffer[j++] = alphabet[((inputBuffer[i] & 0x03) << 4) |
                                     ((remain > 1) ? ((inputBuffer[i + 1] & 0xF0) >> 4): 0)];

        if (remain > 1)
            outputBuffer[j++] = alphabet[((inputBuffer[i + 1] & 0x0F) << 2)
                                         | ((remain > 2) ? ((inputBuffer[i + 2] & 0xC0) >> 6) : 0)];
        else
            outputBuffer[j++] = '=';

        if (remain > 2)
            outputBuffer[j++] = alphabet[inputBuffer[i + 2] & 0x3F];
        else
            outputBuffer[j++] = '=';
    }

    outputBuffer[j] = 0;

    NSString *result = [NSString stringWithCString:outputBuffer length:strlen(outputBuffer)];
    free(outputBuffer);

    return result;
}
@end

Found at http://www.chrisumbel.com/article/basic_authentication_iphone_cocoa_touch