Adding getPrivateKey implementation and tests

Author: jagdish-15

exercises/practice/diffie-hellman/.meta/proof.ci.js

@@ -113,4 +113,8 @@ export class DiffieHellman {
       PRIMES.includes(g)
     );
   }
+
+  static getPrivateKey(p) {
+    return Math.floor(Math.random() * (p - 1) + 2);
+  }
 }

exercises/practice/diffie-hellman/diffie-hellman.js

@@ -15,4 +15,8 @@ export class DiffieHellman {
   getSecret(theirPublicKey, myPrivateKey) {
     throw new Error('Remove this statement and implement this function');
   }
+
+  getPrivateKey() {
+    throw new Error('Remove this statement and implement this function');
+  }
 }

exercises/practice/diffie-hellman/diffie-hellman.spec.js

@@ -87,4 +87,25 @@ describe('diffie-hellman', () => {
 
     expect(secretA).toEqual(secretB);
   });
+
+  xtest('private key is greater than 1 and less than p', () => {
+    let p = 23;
+    for (let i = 0; i < 10; i++) {
+      let privateKey = DiffieHellman.getPrivateKey(p);
+      expect(privateKey).toBeGreaterThan(1);
+      expect(privateKey).toBeLessThan(p);
+    }
+  });
+
+  xtest('private key is random', () => {
+    let p = 7919;
+    let uniqueKeys = new Set();
+    let testIterations = 1000;
+
+    for (let i = 0; i < testIterations; i++) {
+      uniqueKeys.add(DiffieHellman.getPrivateKey(p));
+    }
+
+    expect(uniqueKeys.size).toBeGreaterThan(testIterations - 100);
+  });
 });