diff --git a/gulpfile.js b/gulpfile.js
index e658768..d66ae16 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -23,7 +23,7 @@ gulp.task("pre-coverage", ["coverage-build"], function() {
 });
 
 gulp.task('coverage', ['coverage-build', 'pre-coverage'], function() {
-    return gulp.src("coverage-dist/*.spec.js")
+    return gulp.src("coverage-dist/**/*.spec.js")
         .pipe(jasmine())
         .pipe(istanbul.writeReports({
             dir: './coverage',
@@ -58,7 +58,7 @@ gulp.task('test-build', function() {
 });
 
 gulp.task('test', ['test-build'], function() {
-    return gulp.src("test-dist/*.spec.js")
+    return gulp.src("test-dist/**/*.spec.js")
         .pipe(jasmine());
 });
 
diff --git a/package.json b/package.json
index 30e0f68..877c8da 100644
--- a/package.json
+++ b/package.json
@@ -4,16 +4,18 @@
   "description": "Password generator for BIOS",
   "main": "decrypt_bios.js",
   "dependencies": {
+    "@types/long": "^3.0.32",
     "@types/jasmine": "^2.8.3",
     "gulp-jasmine": "^3.0.0",
-    "typescript": "^2.6.2"
+    "typescript": "^2.6.2",
+    "long": "dcodeIO/long.js"
   },
   "devDependencies": {
     "clean-webpack-plugin": "^0.1.18",
     "copy-webpack-plugin": "^4.3.1",
     "coveralls": "^3.0.0",
-    "gulp": "^3.9.1",
     "del": "^3.0.0",
+    "gulp": "^3.9.1",
     "gulp-istanbul": "^1.1.3",
     "gulp-sourcemaps": "^2.6.4",
     "gulp-tslint": "^8.1.2",
diff --git a/src/keygen/index.ts b/src/keygen/index.ts
index e3a8217..f8b247a 100644
--- a/src/keygen/index.ts
+++ b/src/keygen/index.ts
@@ -1,15 +1,16 @@
+import { monotonicTime } from "../polyfills/performancePolyfill";
 import { asusSolver } from "./asus";
 import { dellHddSolver, dellSolver, hddOldSolver } from "./dell";
 import { fsi20DecNewSolver, fsi20DecOldSolver, fsiHexSolver } from "./fsi";
 import { hpMiniSolver } from "./hpmini";
 import { insydeSolver } from "./insyde";
-import { monotonicTime } from "../polyfills/performancePolyfill";
 import {
     phoenixFsiLSolver, phoenixFsiPSolver, phoenixFsiSolver,
     phoenixFsiSSolver, phoenixFsiXSolver, phoenixHPCompaqSolver, phoenixSolver
 } from "./phoenix";
 import { samsungSolver } from "./samsung";
 import { sonySolver } from "./sony";
+import { sony4x4Solver } from "./sony_4x4";
 import { Solver } from "./utils";
 
 export type KeygenResult = [Solver, string[], number];
@@ -17,6 +18,7 @@ export type KeygenResult = [Solver, string[], number];
 export const solvers: Solver[] = [
     asusSolver,
     sonySolver,
+    sony4x4Solver,
     samsungSolver,
     hddOldSolver,
     dellSolver,
diff --git a/src/keygen/sony_4x4.spec.ts b/src/keygen/sony_4x4.spec.ts
new file mode 100644
index 0000000..2111460
--- /dev/null
+++ b/src/keygen/sony_4x4.spec.ts
@@ -0,0 +1,38 @@
+import * as Long from "long";
+import { modularPow, sony4x4Keygen, sony4x4Solver } from "./sony_4x4";
+
+describe("Sony 4x4 BIOS Keygen", () => {
+    it("Sony 4x4 key for 73KR3FP9PVKHK29R is 32799624", () => {
+        expect(sony4x4Keygen("73KR3FP9PVKHK29R")).toEqual("32799624");
+    });
+    it("Sony 4x4 key for 73KR-3FP9-PVKH-K299 is 69423778", () => {
+        expect(sony4x4Keygen("73KR3FP9PVKHK299")).toEqual("69423778");
+    });
+    it("Sony 4x4 key for 9DPK-73KR-8JHX-F3RT is 54746568", () => {
+        expect(sony4x4Keygen("9DPK73KR8JHXF3RT")).toEqual("54746568");
+    });
+    it("Sony 4x4 key for 3RT6-8JV2-6HX8-K7FX is 32969527", () => {
+        expect(sony4x4Keygen("3RT68JV26HX8K7FX")).toEqual("32969527");
+    });
+    it("Sony 4x4 key for K29R-PVKH-3FP9-73KR is 65395983", () => {
+        expect(sony4x4Keygen("K29RPVKH3FP973KR")).toEqual("65395983");
+    });
+});
+
+describe("Sony 4x4 BIOS Solver", () => {
+    it("Sony 4x4 key for 73KR-3FP9-PVKH-K29R is 32799624", () => {
+        expect(sony4x4Solver("73KR-3FP9-PVKH-K29R")).toEqual(["32799624"]);
+    });
+    it("Sony 4x4 invalid key 73KR-3FP9-PVKH-K29C", () => {
+        expect(sony4x4Solver("73KR-3FP9-PVKH-K29C")).toEqual([]);
+    });
+});
+
+describe("test modularPow", () => {
+    it("4 ^ 13 mod 497 == 445", () => {
+        expect(modularPow(Long.fromInt(4), 13, 497)).toEqual(445);
+    });
+    it("100500 ^ 100500 mod 14 == 8", () => {
+        expect(modularPow(Long.fromInt(100500), 100500, 14)).toEqual(8);
+    });
+});
diff --git a/src/keygen/sony_4x4.ts b/src/keygen/sony_4x4.ts
new file mode 100644
index 0000000..913ae58
--- /dev/null
+++ b/src/keygen/sony_4x4.ts
@@ -0,0 +1,123 @@
+// based on dogbert's pwgen-sony-4x4.py
+/* tslint:disable:no-bitwise */
+import * as Long from "long";
+import { makeSolver } from "./utils";
+
+const otpChars: string = "9DPK7V2F3RT6HX8J";
+const pwdChars: string = "47592836";
+const inputRe: RegExp = new RegExp(`^[${otpChars}]{16}\$`);
+
+function arrayToNumber(arr: number[]): number {
+    // same as python struct.unpack("<I", arr)
+    return (arr[3] << 24 | arr[2] << 16 | arr[1] << 8 | arr[0]) >>> 0;
+}
+
+function numberToArray(num: number): number[] {
+    return [num & 0xFF, (num >> 8) & 0xFF, (num >> 16) & 0xFF, (num >> 24) & 0xFF];
+}
+
+function decodeHash(hash: string): number[] {
+    let temp: number[] = [];
+    for (let i = 0; i < hash.length; i += 2) {
+        // TODO: check values
+        temp.unshift(otpChars.indexOf(hash[i]) * 16 + otpChars.indexOf(hash[i + 1]));
+    }
+    return temp;
+}
+
+function encodePassword(pwd: number[]): string {
+    let n: number = arrayToNumber(pwd);
+    let result: string = "";
+    for (let i = 0; i < 8; i++) {
+        result += pwdChars.charAt((n >> (21 - i * 3)) & 0x7);
+    }
+    return result;
+}
+
+// http://numericalrecipes.blogspot.com/2009/03/modular-multiplicative-inverse.html
+function extEuclideanAlg(a: Long, b: Long): [Long, Long, Long] {
+    if (b.isZero()) {
+        return [new Long(1), new Long(0), a];
+    } else {
+        let [x, y, gcd] = extEuclideanAlg(b, a.mod(b));
+        return [y, x.sub(y.mul(a.div(b))), gcd];
+    }
+}
+
+function modInvEuclid(a: Long, m: Long): Long | undefined {
+    let [x, , gcd] = extEuclideanAlg(a, m);
+    if (gcd.eq(1)) {
+        // hack for javascript modulo operation
+        // https://stackoverflow.com/questions/4467539/javascript-modulo-gives-a-negative-result-for-negative-numbers
+        const temp = x.mod(m);
+        return temp.gte(0) ? temp : temp.add(m);
+    } else {
+        return undefined;
+    }
+}
+
+// https://en.wikipedia.org/wiki/Modular_exponentiation#Right-to-left_binary_method
+export function modularPow(base: Long, exponent: number, modulus: number): number {
+    let result: Long = new Long(1, 0, true);
+
+    if (modulus === 1) {
+        return 0;
+    }
+
+    base = base.mod(modulus);
+
+    while (exponent > 0) {
+        if ((exponent & 1) === 1) {
+           result = result.mul(base).mod(modulus);
+        }
+        exponent = exponent >> 1;
+        base = base.mul(base).mod(modulus);
+    }
+    return result.toNumber();
+}
+
+function rsaDecrypt(code: number[]): number[] {
+    const low: number = arrayToNumber(code.slice(0, 4));
+    const high: number = arrayToNumber(code.slice(4, 8));
+    const c: Long = Long.fromBits(low, high, true);
+
+    const p: number = 2795287379;
+    const q: number = 3544934711;
+    const e = 41;
+    const phi = (new Long(p - 1, 0, true)).mul(q - 1);
+    const d: Long = modInvEuclid(new Long(e), phi) as Long;
+
+    const dp = d.mod(p - 1);
+    const dq = d.mod(q - 1);
+    const qinv: Long = modInvEuclid(new Long(q), new Long(p)) as Long;
+
+    const m1 = modularPow(c, dp.toNumber(), p);
+    const m2 = modularPow(c, dq.toNumber(), q);
+    let h: Long;
+
+    if (m1 < m2) {
+        h = Long.fromValue(m1 - m2).add(p).mul(qinv).mod(p);
+    } else {
+        h = Long.fromValue(m1 - m2).mul(qinv).mod(p);
+    }
+    const m = h.mul(q).add(m2);
+    return numberToArray(m.low).concat(numberToArray(m.high));
+}
+
+export function sony4x4Keygen(hash: string): string {
+    const numHash = decodeHash(hash);
+    const pwd = rsaDecrypt(numHash);
+    return encodePassword(pwd);
+}
+
+export let sony4x4Solver = makeSolver({
+    name: "sony4x4",
+    description: "Sony 4x4",
+    examples: ["73KR-3FP9-PVKH-K29R"],
+    cleaner: (input: string) => input.trim().replace(/[-\s]/gi, "").toUpperCase(),
+    inputValidator: (s) => inputRe.test(s),
+    fun: (code: string) => {
+        let res = sony4x4Keygen(code);
+        return res ? [res] : [];
+    }
+});
diff --git a/src/keygen/utils.ts b/src/keygen/utils.ts
index 60c67b6..fdcadab 100644
--- a/src/keygen/utils.ts
+++ b/src/keygen/utils.ts
@@ -7,6 +7,7 @@ export interface SolverDescription {
     readonly examples?: string[];
     fun: SolverFunction;
     inputValidator: Predicate<string>;
+    cleaner?: (val: string) => string;
 }
 
 export interface Solver {
@@ -75,7 +76,7 @@ function cleanSerial(serial: string): string {
 export function makeSolver(description: SolverDescription): Solver {
 
     let solver: any = (code: string) => {
-        let cleanCode = cleanSerial(code);
+        let cleanCode = solver.cleaner(code);
         if (description.inputValidator(cleanCode)) {
             return description.fun(cleanCode);
         } else {
@@ -85,7 +86,13 @@ export function makeSolver(description: SolverDescription): Solver {
 
     solver.biosName = description.name;
     solver.validator = description.inputValidator;
-    solver.cleaner = cleanSerial;
+
+    if (description.cleaner) {
+        solver.cleaner = description.cleaner;
+    } else {
+        solver.cleaner = cleanSerial;
+    }
+
     solver.keygen = description.fun;
 
     if (description.examples) {