add type definitions for elgamal (#36131)

types/elgamal/elgamal-tests.ts

@@ -0,0 +1,11 @@
+import ElGamal from 'elgamal';
+
+(async () => {
+    const eg = await ElGamal.generateAsync();
+
+    const secret = 'The quick brown fox jumps over the lazy dog';
+    const encrypted = await eg.encryptAsync(secret); // $ExpectType EncryptedValue
+    const decrypted = await eg.decryptAsync(encrypted); // $ExpectType DecryptedValue
+
+    decrypted.toString(); // $ExpectType string
+})();

types/elgamal/index.d.ts

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+// Type definitions for elgamal 0.3
+// Project: https://github.com/kripod/elgamal.js
+// Definitions by: Yu-Hsi Chiang <https://github.com/arbuztw>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+import { BigInteger as BigInt } from 'jsbn';
+
+export default class ElGamal {
+    p: BigInt;
+    g: BigInt;
+    y: BigInt;
+    x: BigInt;
+    static generateAsync(primeBits?: number): Promise<ElGamal>;
+    constructor(p: BigInt | string | number, g: BigInt | string | number, y: BigInt | string | number, x: BigInt | string | number);
+    encryptAsync(m: BigInt | string | number, k?: BigInt | string | number): Promise<EncryptedValue>;
+    decryptAsync(m: EncryptedValue): Promise<DecryptedValue>;
+}
+
+export { BigInt };
+
+export class DecryptedValue {
+    bi: BigInt;
+    constructor(m: BigInt | string | number);
+    toString(): string;
+}
+
+export class EncryptedValue {
+    a: BigInt;
+    b: BigInt;
+    constructor(a: BigInt, b: BigInt);
+    multiply(encryptedValue: EncryptedValue): EncryptedValue;
+}
+
+export namespace Utils {
+    const BIG_TWO: BigInt;
+    function getRandomNbitBigIntAsync(bits: number): Promise<BigInt>;
+    function getRandomBigIntAsync(min: BigInt, max: BigInt): Promise<BigInt>;
+    function getBigPrimeAsync(bits: number): Promise<BigInt>;
+    function parseBigInt(obj: BigInt | string | number): BigInt | null;
+}
+
+export class MissingPrivateKeyError extends Error { }

types/elgamal/tsconfig.json

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+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "target": "es6",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictFunctionTypes": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "elgamal-tests.ts"
+    ]
+}

types/elgamal/tslint.json

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+{ "extends": "dtslint/dt.json" }