dosyspongeaont/index.js

reversible all-or-nothing package transform using dosysponge

"use strict";
{
  const sponge = require('dosysponge');
  const BLOCK_SIZE_OCTETS = 512;
  const RATE = BLOCK_SIZE_OCTETS;
  const CAPACITY = 22;              // total state size of sponge is rate * capacity
  const SHIFT = 3;

  const dosyspongeaont = {
    aont, pad, chunk
  };

  try { module.exports = dosyspongeaont; } catch(e) { Object.assign( self, { dosysponeagont } ); }

  function aont( m, { inverse : inverse = false } = {}) {
    console.log( inverse );
    const s = sponge_instance();
    const c = chunk( pad( m, {inverse} ) );
    const first_cover = s.squeeze( 512, { out_format : 'bytes' , iterations: 8 });
    const output = new Array();
    let cover = first_cover;
    for( const chunk of c ) {
      const block = xor( chunk, cover );
      if ( inverse ) {
        s.absorb( block );
      } else {
        s.absorb( chunk );
      }
      cover = s.squeeze( 512, { out_format: 'bytes' } );
      output.push( block );
    }
    let result = output.join('');
    if ( inverse ) {
      result = result.slice(BLOCK_SIZE_OCTETS,-BLOCK_SIZE_OCTETS);
    }
    return result;
  }

  function xor( mc = '', bytes = new Uint8Array ) {
    // FIXME: does not work with Unicode
    const mb = mc.split('').map( c => c.codePointAt(0) );
    mb.forEach( (v,i) => {
      mb[i] ^= bytes[i];
    });
    return mb.map( v => String.fromCodePoint(v) ).join('');
  }

  function sponge_instance() {
    const [rate, capacity, shift] = [RATE, CAPACITY, SHIFT];
    return new sponge.DosySponge( { rate, capacity, shift } );
  }

  function pad( m, { inverse } ) {
    const p = (BLOCK_SIZE_OCTETS - (m.length % BLOCK_SIZE_OCTETS)) % BLOCK_SIZE_OCTETS;
    let padding = '';
    if ( ! inverse ) {
      padding = new Array(BLOCK_SIZE_OCTETS+1).join('0');
    }
    return padding + m + (new Array(p+1).join('0')) + padding;
  }

  function chunk( m ) {
    return m.split('').reduce( (C,mc,i) => {
      if ( i % BLOCK_SIZE_OCTETS ) {
        C[C.length-1] += mc;
      } else {
        C.push(mc);
      }
      return C;
    }, []);
  }
}