circuit: add email nullifier helper

zkemail · Mar 30, 2024 · 0d29c5b · 0d29c5b
1 parent b9ce992
commit 0d29c5b
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Showing 3 changed files with 25 additions and 2 deletions.
diff --git a/packages/circuits/email-verifier.circom b/packages/circuits/email-verifier.circom
@@ -116,6 +116,7 @@ template EmailVerifier(maxHeaderLength, maxBodyLength, n, k, ignoreBodyHashCheck
 
     // Calculate the Poseidon hash of DKIM public key as output
     // This can be used to verify (by verifier/contract) the pubkey used in the proof without needing the full key
+    // Since PoseidonLarge concatenates nearby values its important to use same n/k (recommended 121*17) to produce uniform hashes
     // https://zkrepl.dev/?gist=43ce7dce2466c63812f6efec5b13aa73 - This can be used to calculate the pubkey hash separately
     pubkeyHash <== PoseidonLarge(n, k)(pubkey);
 }
diff --git a/packages/circuits/helpers/email-nullifier.circom b/packages/circuits/helpers/email-nullifier.circom
@@ -0,0 +1,22 @@
+
+pragma circom 2.1.5;
+
+include "circomlib/circuits/poseidon.circom";
+
+
+/// @title EmailNullifier
+/// @notice An opinionated way of calculating the email nullifier
+/// @notice nullifier = poseidon(poseidon(signature))
+/// @param bitPerChunk The number of bits per chunk the signature is split into
+/// @param chunkSize The number of chunks the signature is split into
+/// @input signature The signature of the email
+/// @output out The email nullifier
+template EmailNullifier(bitPerChunk, chunkSize) {
+    signal input signature[chunkSize];
+
+    signal output out;
+
+    signal signatureHash <== PoseidonLarge(bitPerChunk, chunkSize)(signature);
+
+    out <== Poseidon(1)([signatureHash]);
+}
diff --git a/packages/circuits/utils/extract.circom b/packages/circuits/utils/extract.circom
@@ -5,7 +5,7 @@ include "circomlib/circuits/bitify.circom";
 include "./bytes.circom";
 
 /// @title ExtractRegexReveal
-/// @dev Extracts reveal part from a regex match
+/// @notice Extracts reveal part from a regex match
 /// @param maxArrayLen Maximum length of the input array
 /// @param maxRevealLen Maximum length of the reveal part
 /// @input in Input array
@@ -50,7 +50,7 @@ template ExtractRegexReveal(maxArrayLen, maxRevealLen) {
 
 
 /// @title PackRegexReveal
-/// @dev Packs reveal data from a regex match into int[]
+/// @notice Packs reveal data from a regex match into int[]
 /// @param maxArrayLen Maximum length of the input array
 /// @param maxRevealLen Maximum length of the reveal part
 /// @input in Input array