diff --git a/contracts/StorageContract.sol b/contracts/StorageContract.sol
index dc0b755..8212c5d 100644
--- a/contracts/StorageContract.sol
+++ b/contracts/StorageContract.sol
@@ -13,6 +13,8 @@ contract StorageContract {
   uint public immutable proofTimeout; // proof has to be submitted before this
   uint public immutable proofMarker; // indicates when a proof is required
 
+  mapping(uint => bool) proofReceived; // whether proof for a block was received
+
   constructor(uint _duration,
               uint _size,
               bytes32 _contentHash,
@@ -101,4 +103,15 @@ contract StorageContract {
     bytes32 hash = blockhash(blocknumber);
     return hash != 0 && uint(hash) % proofPeriod == proofMarker;
   }
+
+  function submitProof(uint blocknumber, bool proof) public {
+    require(proof, "Invalid proof"); // TODO: replace bool by actual proof
+    require(isProofRequired(blocknumber), "No proof required for this block");
+    require(
+      block.number < blocknumber + proofTimeout,
+      "Proof not allowed after timeout"
+    );
+    require(!proofReceived[blocknumber], "Proof already submitted");
+    proofReceived[blocknumber] = true;
+  }
 }
diff --git a/test/StorageContract.test.js b/test/StorageContract.test.js
index 511672c..18f84cb 100644
--- a/test/StorageContract.test.js
+++ b/test/StorageContract.test.js
@@ -186,13 +186,56 @@ describe("Storage Contract", function () {
       expect(await contract.isProofRequired(blocknumber)).to.be.false
     })
 
+    it("submits a correct proof", async function () {
+      await mineUntilProofIsRequired()
+      let blocknumber = await minedBlockNumber()
+      await contract.submitProof(blocknumber, true)
+    })
+
+    it("fails proof submission when proof is incorrect", async function () {
+      await mineUntilProofIsRequired()
+      let blocknumber = await minedBlockNumber()
+      await expect(
+        contract.submitProof(blocknumber, false)
+      ).to.be.revertedWith("Invalid proof")
+    })
+
+    it("fails proof submission when proof was not required", async function () {
+      while (await contract.isProofRequired(await minedBlockNumber())) {
+        await mineBlock()
+      }
+      let blocknumber = await minedBlockNumber()
+      await expect(
+        contract.submitProof(blocknumber, true)
+      ).to.be.revertedWith("No proof required")
+    })
+
+    it("fails proof submission when proof is too late", async function () {
+      await mineUntilProofIsRequired()
+      let blocknumber = await minedBlockNumber()
+      for (let i=0; i<proofTimeout; i++) {
+        mineBlock()
+      }
+      await expect(
+        contract.submitProof(blocknumber, true)
+      ).to.be.revertedWith("Proof not allowed after timeout")
+    })
+
+    it("fails proof submission when already submitted", async function() {
+      await mineUntilProofIsRequired()
+      let blocknumber = await minedBlockNumber()
+      await contract.submitProof(blocknumber, true)
+      await expect(
+        contract.submitProof(blocknumber, true)
+      ).to.be.revertedWith("Proof already submitted")
+    })
   })
 })
 
+// TODO: implement checking of actual proofs of storage, instead of dummy bool
 // TODO: payment on constructor
 // TODO: contract start and timeout
 // TODO: missed proofs
-// TODO: successfull proofs
 // TODO: only allow proofs after start of contract
 // TODO: payout
 // TODO: stake