From dec28e16d4457397371112bab42c2b28fb86c461 Mon Sep 17 00:00:00 2001
From: mshwed <m@ttshwed.com>
Date: Fri, 5 Apr 2019 11:12:44 -0400
Subject: [PATCH] Added histogram visualization for text entropy

---
 src/core/operations/AdvancedEntropy.mjs | 180 ++++++++++++++++++++++++
 1 file changed, 180 insertions(+)
 create mode 100644 src/core/operations/AdvancedEntropy.mjs

diff --git a/src/core/operations/AdvancedEntropy.mjs b/src/core/operations/AdvancedEntropy.mjs
new file mode 100644
index 00000000..b3316583
--- /dev/null
+++ b/src/core/operations/AdvancedEntropy.mjs
@@ -0,0 +1,180 @@
+/**
+ * @author mshwed [m@ttshwed.com]
+ * @copyright Crown Copyright 2019
+ * @license Apache-2.0
+ */
+
+import * as d3temp from "d3";
+import * as nodomtemp from "nodom";
+
+import Operation from "../Operation";
+import Utils from "../Utils";
+
+const d3 = d3temp.default ? d3temp.default : d3temp;
+const nodom = nodomtemp.default ? nodomtemp.default: nodomtemp;
+
+/**
+ * Advanced Entropy operation
+ */
+class AdvancedEntropy extends Operation {
+
+    /**
+     * AdvancedEntropy constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Advanced Entropy";
+        this.module = "Default";
+        this.description = "Adds advanced views for examining entropy";
+        this.infoURL = "";
+        this.inputType = "byteArray";
+        this.outputType = "html";
+        this.presentType = "html";
+        this.args = [];
+    }
+
+    /**
+     * Calculates the frequency of bytes in the input.
+     * 
+     * @param {byteArray} input
+     * @returns {frequency}
+     */
+    calculateShannonEntropy(input) {
+        const prob = [],
+        uniques = input.unique(),
+        str = Utils.byteArrayToChars(input);
+        let i;
+
+        for (i = 0; i < uniques.length; i++) {
+            prob.push(str.count(Utils.chr(uniques[i])) / input.length);
+        }
+
+        let entropy = 0,
+            p;
+
+        for (i = 0; i < prob.length; i++) {
+            p = prob[i];
+            entropy += p * Math.log(p) / Math.log(2);
+        }
+
+        return -entropy;
+    }
+
+    /**
+     * Calculates the frequency of bytes in the input.
+     * 
+     * @param {byteArray} inputBytes
+     * @returns {frequency}
+     */
+    calculateByteFrequency(inputBytes) {
+        console.log(inputBytes);
+
+        let byteFrequency = [];
+        for (let i = 0; i < 256; i++) {
+            let count = 0;
+            for (let byte of inputBytes) {
+                if (byte === i) {
+                    count++;
+                }
+            }
+
+            byteFrequency.push(count / (inputBytes.length + 1))
+        }
+
+        return byteFrequency;
+    }
+
+    /**
+     * Creates a byte frequency histogram
+     * 
+     * @param {byteArray} entropyData
+     * @returns {HTML}
+     */
+    createByteFrequencyHistogram(entropyData) {
+        const byteFrequency = entropyData.byteFrequency;
+
+        const svgWidth = 500,
+            svgHeight = 500,
+            binWidth = 1;
+
+        const document = new nodom.Document();
+        let svg = document.createElement("svg");
+        svg = d3.select(svg)
+            .attr("width", "100%")
+            .attr("height", "100%")
+            .attr("viewBox", `0 0 ${svgWidth} ${svgHeight}`);
+        
+        const margins = {top: 30, right: 20, bottom: 50, left: 30};
+
+        const yScale = d3.scaleLinear()
+            .domain(d3.extent(byteFrequency, d => d))
+            .range([svgHeight - margins.bottom, margins.top])
+
+        const xScale = d3.scaleLinear()
+            .domain([0, byteFrequency.length - 1])
+            .range([margins.left - binWidth, svgWidth - margins.right])
+
+        svg.selectAll("rect")
+            .data(byteFrequency)
+            .enter().append("rect")
+            .attr("x", (_, i) => xScale(i) + binWidth)
+            .attr("y", (dataPoint) => yScale(dataPoint))
+            .attr("width", binWidth)
+            .attr("height", dataPoint => yScale(0) - yScale(dataPoint))
+            .attr("fill", "blue")
+
+        // Axes
+        const yAxis = d3.axisLeft()
+            .scale(yScale);
+
+        const xAxis = d3.axisBottom()
+            .scale(xScale)
+
+        svg.append("g")
+            .attr("transform", `translate(${binWidth}, ${svgHeight - margins.bottom})`)
+            .call(xAxis);
+
+        svg.append("g")
+            .attr("transform", `translate(${margins.left},0)`)
+            .call(yAxis);
+
+        // Axes labels
+        svg.append("text")
+            .attr("transform", "rotate(-90)")
+            .attr("y", 0 - margins.left)
+            .attr("x", 0 - (svgHeight / 2))
+            .attr("dy", "1em")
+            .style("text-anchor", "middle")
+            .text("Frequency (%)")
+
+        svg.append("text")
+            .attr("transform", `translate(${svgWidth / 2}, ${svgHeight - margins.bottom + 40})`)
+            .style("text-anchor", "middle")
+            .text("Byte")
+
+        // Add title
+        svg.append("text")
+            .attr("transform", `translate(${svgWidth / 2}, ${margins.top - 10})`)
+            .style("text-anchor", "middle")
+            .text("Byte Frequency")
+
+        return svg._groups[0][0].outerHTML;
+    }
+
+    /**
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {html}
+     */
+    run(input, args) {       
+        const entropyData = {
+            entropy: this.calculateShannonEntropy(input),
+            byteFrequency: this.calculateByteFrequency(input) 
+        }; 
+        let svgData = this.createByteFrequencyHistogram(entropyData)
+       return svgData
+    }
+}
+
+export default AdvancedEntropy;