Add PoW module

src/pow/pow.service.ts

@@ -0,0 +1,88 @@
+import { CACHE_MANAGER } from '@nestjs/cache-manager';
+import { Inject, Injectable, Logger } from '@nestjs/common';
+import { Cache } from 'cache-manager';
+import { randomBytes, createHash } from 'crypto';
+
+
+@Injectable()
+export class PowService {
+    private readonly logger = new Logger(PowService.name);
+    private difficulty = 5;
+
+    constructor(
+        @Inject(CACHE_MANAGER) private cacheManager: Cache,
+    ) { }
+
+    /**
+     * Generate a proof of work challenge, stored to redis for verification within
+     * the next 10 seconds.
+     */
+    async generateChallenge() {
+        const challenge = this.generateRandom256BitString();
+        console.log(challenge)
+        await this.cacheManager.set(challenge, true, 60 * 1000);
+        return challenge;
+    }
+
+    generateRandom256BitString() {
+        const randomString = randomBytes(32).toString('hex');
+        return randomString;
+    }
+
+
+    hashAndCheck(string: string) {
+        return this.hashPassesDifficulty(this.hashString(string), this.difficulty);
+    }
+
+    hashPassesDifficulty(hash: string, difficulty: number) {
+        return hash.startsWith('0'.repeat(difficulty));
+    }
+
+    /**
+     * Verify that the proof of work submitted has a leading number of
+     * zeroes equal to the challenge length and the challenge exists.
+     */
+    async verifyChallenge(challenge: string, proof: string): Promise<boolean> {
+        const expected = await this.cacheManager.get<boolean>(challenge);
+        return expected ? this.hashAndCheck(proof + challenge) : false;
+    }
+
+    async markChallengeAsComplete(challenge: string) {
+        await this.cacheManager.del(challenge);
+    }
+
+    /**
+     * Perform a proof of work challenge to find a proof that hashes to a value
+     */
+    async performChallenge(challenge: string) {
+        let proof = this.generateRandom256BitString();
+        let hash = this.hashString(proof + challenge);
+        while (!this.hashPassesDifficulty(hash, this.difficulty)) {
+            proof = this.generateRandom256BitString();
+            hash = this.hashString(proof + challenge);
+        }
+        return { proof, hash };
+    }
+
+    /**
+     * sha512 the provided string and return the result.
+     */
+    hashString(input: string) {
+        return createHash('sha512').update(input).digest('hex');
+    }
+
+    /**
+     * Set the difficulty of the proof of work challenge.
+     */
+    setDifficulty(difficulty: number) {
+        this.difficulty = difficulty;
+    }
+
+    /**
+     * Get the current difficulty of the proof of work challenge.
+     */
+    getDifficulty() {
+        return this.difficulty;
+    }
+
+}