diff --git a/.yarn/install-state.gz b/.yarn/install-state.gz
new file mode 100644
index 00000000..4940bd19
Binary files /dev/null and b/.yarn/install-state.gz differ
diff --git a/Week19/randomness/contracts/PseudoRandom b/Week19/randomness/contracts/PseudoRandom
new file mode 100644
index 00000000..1542284e
--- /dev/null
+++ b/Week19/randomness/contracts/PseudoRandom
@@ -0,0 +1,102 @@
+//SPDX-License-Identifier: MIT
+pragma solidity >=0.7.0 <0.9.0;
+
+import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
+
+contract PseudoRandom {
+    using ECDSA for bytes32;
+
+    struct Signature {
+        uint8 v;
+        bytes32 r;
+        bytes32 s;
+    }
+
+    Signature savedSig;
+
+    function setSignature(
+        uint8 _v,
+        bytes32 _r,
+        bytes32 _s
+    ) public {
+        savedSig = Signature({v: _v, r: _r, s: _s});
+    }
+
+    function getRandomNumber(string calldata seed)
+        public
+        view
+        returns (uint256 pseudoRandomNumber)
+    {
+        address messageSigner = verifyString(
+            seed,
+            savedSig.v,
+            savedSig.r,
+            savedSig.s
+        );
+        require(msg.sender == messageSigner, "Invalid seed");
+        pseudoRandomNumber = uint256(keccak256(abi.encodePacked(seed)));
+    }
+
+    function getCombinedRandomNumber(string calldata seed)
+        public
+        view
+        returns (uint256 pseudoRandomNumber)
+    {
+        address messageSigner = verifyString(
+            seed,
+            savedSig.v,
+            savedSig.r,
+            savedSig.s
+        );
+        require(msg.sender == messageSigner, "Invalid seed");
+        pseudoRandomNumber = uint256(
+            keccak256(abi.encodePacked(seed, blockhash(block.number - 1)))
+        );
+    }
+
+    // Don't worry about this function for now
+    function verifyString(
+        string memory message,
+        uint8 v,
+        bytes32 r,
+        bytes32 s
+    ) public pure returns (address signer) {
+        string memory header = "\x19Ethereum Signed Message:\n000000";
+        uint256 lengthOffset;
+        uint256 length;
+        assembly {
+            length := mload(message)
+            lengthOffset := add(header, 57)
+        }
+        require(length <= 999999);
+        uint256 lengthLength = 0;
+        uint256 divisor = 100000;
+        while (divisor != 0) {
+            uint256 digit = length / divisor;
+            if (digit == 0) {
+                if (lengthLength == 0) {
+                    divisor /= 10;
+                    continue;
+                }
+            }
+            lengthLength++;
+            length -= digit * divisor;
+            divisor /= 10;
+            digit += 0x30;
+            lengthOffset++;
+            assembly {
+                mstore8(lengthOffset, digit)
+            }
+        }
+        if (lengthLength == 0) {
+            lengthLength = 1 + 0x19 + 1;
+        } else {
+            lengthLength += 1 + 0x19;
+        }
+        assembly {
+            mstore(header, lengthLength)
+        }
+        bytes32 check = keccak256(abi.encodePacked(header, message));
+        return ecrecover(check, v, r, s);
+    }
+}
\ No newline at end of file
diff --git a/Week19/randomness/contracts/Random.sol b/Week19/randomness/contracts/Random.sol
new file mode 100644
index 00000000..3b3ac49c
--- /dev/null
+++ b/Week19/randomness/contracts/Random.sol
@@ -0,0 +1,13 @@
+contract Random {
+    function getRandomNumber()
+        public
+        view
+        returns (uint256 randomNumber)
+    {
+        // TODO: get randomness from previous block randao reveal
+    }
+
+    function tossCoin() public view returns (bool heads) {
+        // TODO: make the random number be translated to a boolean
+    }
+}
\ No newline at end of file
diff --git a/Week19/randomness/scripts/TestPseudoRandom.ts b/Week19/randomness/scripts/TestPseudoRandom.ts
new file mode 100644
index 00000000..ee799a7b
--- /dev/null
+++ b/Week19/randomness/scripts/TestPseudoRandom.ts
@@ -0,0 +1,109 @@
+import { ethers } from "ethers";
+
+async function signature() {
+  const signers = await ethers.getSigners();
+  const signer = signers[0];
+  console.log(
+    `Signing a message with the account of address ${signer.address}`
+  );
+  const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout,
+  });
+  rl.question("Enter a message to be signed:\n", async (answer) => {
+    const signedMessage = await signer.signMessage(answer);
+    console.log(`The signed message is:\n${signedMessage}`);
+    rl.close();
+    testSignature();
+  });
+}
+
+async function testSignature() {
+  console.log("Verifying signature\n");
+  const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout,
+  });
+  rl.question("Enter message signature:\n", (signature) => {
+    rl.question("Enter message:\n", (message) => {
+      const address = ethers.utils.verifyMessage(message, signature);
+      console.log(`This message signature matches with address ${address}`);
+      rl.question("Repeat? [Y/N]:\n", (answer) => {
+        rl.close();
+        if (answer.toLowerCase() === "y") {
+          testSignature();
+        }
+      });
+    });
+  });
+}
+
+async function sealedSeed() {
+  console.log("Deploying contract");
+  const contractFactory = await ethers.getContractFactory("PseudoRandom");
+  const contract: PseudoRandom = await contractFactory.deploy();
+  await contract.deployed();
+  const signers = await ethers.getSigners();
+  const signer = signers[0];
+  console.log(
+    `Signing a message with the account of address ${signer.address}`
+  );
+  const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout,
+  });
+  rl.question("Enter a random seed to be signed:\n", async (seed) => {
+    const signedMessage = await signer.signMessage(seed);
+    rl.close();
+    console.log(`The signed message is:\n${signedMessage}`);
+    const sig = ethers.utils.splitSignature(signedMessage);
+    console.log("Saving signature at contract");
+    await contract.setSignature(sig.v, sig.r, sig.s);
+    try {
+      console.log("Trying to get a number with the original seed");
+      const randomNumber = await contract.getRandomNumber(seed);
+      console.log(`Random number result:\n${randomNumber}`);
+      console.log("Trying to get a number without the original seed");
+      const fakeSeed = "FAKE_SEED";
+      const randomNumber2 = await contract.getRandomNumber(fakeSeed);
+      console.log(`Random number result:\n${randomNumber2}`);
+    } catch (error) {
+      console.log("Operation failed");
+    }
+  });
+}
+
+async function randomSealedSeed() {
+  console.log("Deploying contract");
+  const contractFactory = await ethers.getContractFactory("PseudoRandom");
+  const contract: PseudoRandom = await contractFactory.deploy();
+  await contract.deployed();
+  const signers = await ethers.getSigners();
+  const signer = signers[0];
+  console.log(
+    `Signing a message with the account of address ${signer.address}`
+  );
+  const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout,
+  });
+  rl.question("Enter a random seed to be signed:\n", async (seed) => {
+    const signedMessage = await signer.signMessage(seed);
+    rl.close();
+    console.log(`The signed message is:\n${signedMessage}`);
+    const sig = ethers.utils.splitSignature(signedMessage);
+    console.log("Saving signature at contract");
+    await contract.setSignature(sig.v, sig.r, sig.s);
+    try {
+      console.log("Trying to get a number with the original seed");
+      const randomNumber = await contract.getCombinedRandomNumber(seed);
+      console.log(`Random number result:\n${randomNumber}`);
+      console.log("Trying to get a number without the original seed");
+      const fakeSeed = "FAKE_SEED";
+      const randomNumber2 = await contract.getCombinedRandomNumber(fakeSeed);
+      console.log(`Random number result:\n${randomNumber2}`);
+    } catch (error) {
+      console.log("Operation failed");
+    }
+  });
+}
\ No newline at end of file
diff --git a/Week19/randomness/scripts/TestRandom.ts b/Week19/randomness/scripts/TestRandom.ts
index 97851ccf..e413548f 100644
--- a/Week19/randomness/scripts/TestRandom.ts
+++ b/Week19/randomness/scripts/TestRandom.ts
@@ -21,16 +21,16 @@ async function main() {
             tossCoin();
             break;
           case 3:
-            // signature();
+            signature();
             break;
           case 4:
-            // sealedSeed();
+            sealedSeed();
             break;
           case 5:
-            // randomSealedSeed();
+            randomSealedSeed();
             break;
           case 6:
-            // randao();
+            randao();
             break;
           default:
             console.log("Invalid");
diff --git a/Week19/randomness/scripts/TestRandomAgain.ts b/Week19/randomness/scripts/TestRandomAgain.ts
new file mode 100644
index 00000000..6e95aeda
--- /dev/null
+++ b/Week19/randomness/scripts/TestRandomAgain.ts
@@ -0,0 +1,36 @@
+async function randao() {
+    const contractFactory = await ethers.getContractFactory("Random");
+    contractFactory.deploy().then(async (result) => {
+      result.deployed().then(async (contract: Random) => {
+        const currentBlock = await ethers.provider.getBlock("latest");
+        const randomNumber = await contract.getRandomNumber();
+        console.log(
+          `Block number: ${currentBlock.number}\nBlock difficulty: ${currentBlock.difficulty}\nRandom number from this block difficulty: ${randomNumber}`
+        );
+        await ethers.provider.send("evm_mine", [currentBlock.timestamp + 1]);
+        const currentBlock2 = await ethers.provider.getBlock("latest");
+        const randomNumber2 = await contract.getRandomNumber();
+        console.log(
+          `Block number: ${currentBlock2.number}\nBlock difficulty: ${currentBlock2.difficulty}\nRandom number from this block difficulty: ${randomNumber2}`
+        );
+        await ethers.provider.send("evm_mine", [currentBlock2.timestamp + 1]);
+        const currentBlock3 = await ethers.provider.getBlock("latest");
+        const randomNumber3 = await contract.getRandomNumber();
+        console.log(
+          `Block number: ${currentBlock3.number}\nBlock difficulty: ${currentBlock3.difficulty}\nRandom number from this block difficulty: ${randomNumber3}`
+        );
+        await ethers.provider.send("evm_mine", [currentBlock3.timestamp + 1]);
+        const currentBlock4 = await ethers.provider.getBlock("latest");
+        const randomNumber4 = await contract.getRandomNumber();
+        console.log(
+          `Block number: ${currentBlock4.number}\nBlock difficulty: ${currentBlock4.difficulty}\nRandom number from this block difficulty: ${randomNumber4}`
+        );
+        await ethers.provider.send("evm_mine", [currentBlock4.timestamp + 1]);
+        const currentBlock5 = await ethers.provider.getBlock("latest");
+        const randomNumber5 = await contract.getRandomNumber();
+        console.log(
+          `Block number: ${currentBlock5.number}\nBlock difficulty: ${currentBlock5.difficulty}\nRandom number from this block difficulty: ${randomNumber5}`
+        );
+      });
+    });
+  }
\ No newline at end of file
diff --git a/node_modules/.yarn-integrity b/node_modules/.yarn-integrity
new file mode 100644
index 00000000..56c28ed9
--- /dev/null
+++ b/node_modules/.yarn-integrity
@@ -0,0 +1,10 @@
+{
+  "systemParams": "win32-x64-108",
+  "modulesFolders": [],
+  "flags": [],
+  "linkedModules": [],
+  "topLevelPatterns": [],
+  "lockfileEntries": {},
+  "files": [],
+  "artifacts": {}
+}
\ No newline at end of file
diff --git a/node_modules/.yarn-state.yml b/node_modules/.yarn-state.yml
new file mode 100644
index 00000000..7ee72942
--- /dev/null
+++ b/node_modules/.yarn-state.yml
@@ -0,0 +1,10 @@
+# Warning: This file is automatically generated. Removing it is fine, but will
+# cause your node_modules installation to become invalidated.
+
+__metadata:
+  version: 1
+  nmMode: classic
+
+"root-workspace-0b6124@workspace:.":
+  locations:
+    - ""
diff --git a/package.json b/package.json
new file mode 100644
index 00000000..0967ef42
--- /dev/null
+++ b/package.json
@@ -0,0 +1 @@
+{}
diff --git a/yarn.lock b/yarn.lock
new file mode 100644
index 00000000..722dc367
--- /dev/null
+++ b/yarn.lock
@@ -0,0 +1,11 @@
+# This file is generated by running "yarn install" inside your project.
+# Manual changes might be lost - proceed with caution!
+
+__metadata:
+  version: 6
+
+"root-workspace-0b6124@workspace:.":
+  version: 0.0.0-use.local
+  resolution: "root-workspace-0b6124@workspace:."
+  languageName: unknown
+  linkType: soft