Overview

The CPI Online result data is encoded into a URL. The software that performs this function is cpi.Code.

Code

The coding functions are the following.

    String Encode(float nt, float nf, float st, float sf){
        return Hex(Pad(Bits(nt,nf,st,sf)));
    }
    float[] Decode(String string){
        return Bits(Pad(Hex(string)));
    }

The Pad function is a well known cipher, used with a known key to scramble the binary results data.

    byte[] Pad = {
        'L', 'o', 'r', 'e', 'm', ' ', 'i', 'p', 's', 'u', 'm', ' ', 'd', 'o', 'l', 
        'o', 'r', ' ', 's', 'i', 't', ' ', 'a', 'm', 'e', 't', ',', ' ', 'c', 'o', 
    };

    byte[] Pad(byte[] text){
        int len = text.length;
        byte[] re = new byte[len];
        for (int cc = 0; cc < len; cc++){

           re[cc] = (byte)(text[cc] ^ Pad[cc]);
        }
        return re;
    }

The Bits function performs a 16 bit encoding and decoding of the quadrant values. It does this using a fixed point representation for the values, known to exist between zero and one and needing only a modest (1e-4) margin of error.

    float FX = 0xffff;

    byte[] Bits(float nt, float nf, float st, float sf){

        int b_nt = (int)(nt*FX);
        int b_nf = (int)(nf*FX);
        int b_st = (int)(st*FX);
        int b_sf = (int)(sf*FX);

        byte[] re = new byte[8];
        re[0] = (byte)((b_nt>>8) & 0xff);
        re[1] = (byte)(b_nt & 0xff);
        re[2] = (byte)((b_nf>>8) & 0xff);
        re[3] = (byte)(b_nf & 0xff);
        re[4] = (byte)((b_st>>8) & 0xff);
        re[5] = (byte)(b_st & 0xff);
        re[6] = (byte)((b_sf>>8) & 0xff);
        re[7] = (byte)(b_sf & 0xff);
        return re;
    }
    float[] Bits(byte[] bits){

        float b_nt = (((bits[0] & 0xff)<<8)|(bits[1] & 0xff));
        float b_nf = (((bits[2] & 0xff)<<8)|(bits[3] & 0xff));
        float b_st = (((bits[4] & 0xff)<<8)|(bits[5] & 0xff));
        float b_sf = (((bits[6] & 0xff)<<8)|(bits[7] & 0xff));

        return new float[]{
            (b_nt/FX),
            (b_nf/FX),
            (b_st/FX),
            (b_sf/FX)
        };
    }

Plain text

The plain text embedded in this code is a binary 16 bit fixed point representation of the four CPI Quadrant values: NT, NF, ST, and SF.

Eyeballs Privacy

We hope that most people will want to share their CPI Online results with others. Sharing can be a powerful aid.

But first we recognize our responsibility to provide a basic degree of privacy for any form of personal data, including the anonymous CPI Online result.

As the result URL is intended to be saved, the URL itself does not reveal any personal data to a casual glance at it.

This is eyeballs privacy.

One must have a copy of the URL, and decode the URL, in order to have the CPI result data.