diff --git a/src/circuit-wrapper.ts b/src/circuit-wrapper.ts
index 96da242f..52f5ae6b 100644
--- a/src/circuit-wrapper.ts
+++ b/src/circuit-wrapper.ts
@@ -75,6 +75,10 @@ export class RLNProver {
     x: bigint;
     epoch: bigint;
   }): Promise<RLNFullProof> {
+    if (args.x <= BigInt(0)) {
+      // y = identitySecret + a1 * x
+      throw new Error('identity secret is directly leaked if x = 0')
+    }
     const witness: RLNWitness = {
       identitySecret: args.identitySecret,
       userMessageLimit: args.userMessageLimit,
diff --git a/src/contract-wrapper.ts b/src/contract-wrapper.ts
index 48934f30..aee05ca9 100644
--- a/src/contract-wrapper.ts
+++ b/src/contract-wrapper.ts
@@ -90,10 +90,6 @@ export class RLNContract {
     return this.signer || this.provider
   }
 
-  async getTokenAddress() {
-    return this.rlnContract.token()
-  }
-
   async getSignerAddress() {
     if (this.signer === undefined) {
       throw new Error('Cannot get signer address if signer is not set')
@@ -101,6 +97,30 @@ export class RLNContract {
     return this.signer.getAddress()
   }
 
+  async getMinimalDeposit() {
+    return this.rlnContract.MINIMAL_DEPOSIT()
+  }
+
+  async getMaximalRate() {
+    return this.rlnContract.MAXIMAL_RATE()
+  }
+
+  async getFeeReceiver() {
+    return this.rlnContract.FEE_RECEIVER()
+  }
+
+  async getFeePercentage() {
+    return this.rlnContract.FEE_PERCENTAGE()
+  }
+
+  async getFreezePeriod() {
+    return this.rlnContract.FREEZE_PERIOD()
+  }
+
+  async getTokenAddress() {
+    return this.rlnContract.token()
+  }
+
   async getLogs() {
     const rlnContractAddress = await this.rlnContract.getAddress()
     const currentBlockNumber = await this.provider.getBlockNumber()
@@ -160,8 +180,11 @@ export class RLNContract {
       erc20ABI,
       this.getContractRunner(),
     )
-    const txApprove = await tokenContract.approve(rlnContractAddress, amount)
-    await txApprove.wait()
+    const allowance = await tokenContract.allowance(await this.getSignerAddress(), rlnContractAddress)
+    if (allowance < amount) {
+      const txApprove = await tokenContract.approve(rlnContractAddress, amount)
+      await txApprove.wait()
+    }
     const txRegister = await this.rlnContract.register(identityCommitment, amount)
     const receipt = await txRegister.wait()
     return receipt
diff --git a/src/registry.ts b/src/registry.ts
index 71e9feea..2c253cfe 100644
--- a/src/registry.ts
+++ b/src/registry.ts
@@ -137,6 +137,9 @@ export class ContractRLNRegistry implements IRLNRegistry {
       identitySecret,
       address: userAddressBigInt,
     })
+    if (identityCommitment != BigInt(proof.publicSignals[0]) || userAddressBigInt != BigInt(proof.publicSignals[1])) {
+      throw new Error('Withdraw proof public signals do not match')
+    }
     await this.rlnContract.withdraw(identityCommitment, proof.proof)
   }
 
@@ -163,6 +166,9 @@ export class ContractRLNRegistry implements IRLNRegistry {
       identitySecret,
       address: receiverBigInt,
     })
+    if (identityCommitment != BigInt(proof.publicSignals[0]) || receiverBigInt != BigInt(proof.publicSignals[1])) {
+      throw new Error('Withdraw proof public signals do not match')
+    }
     await this.rlnContract.slash(identityCommitment, receiver, proof.proof)
   }
 }