From f49eb3ed46ad47c416985c18874fc9a071691ef4 Mon Sep 17 00:00:00 2001
From: Neale Pickett <neale.pickett@pnnl.gov>
Date: Fri, 15 Sep 2023 12:34:31 -0600
Subject: [PATCH] =?UTF-8?q?Change=20answer=20hash=20algorithm=20to=20SHA1?=
 =?UTF-8?q?=E2=82=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 CHANGELOG.md                 | 4 ++--
 pkg/transpile/puzzle.go      | 6 +++---
 pkg/transpile/puzzle_test.go | 6 ++++++
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9fc8422..5fd80c8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,8 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [v4.6.0] - unreleased
 ### Changed
-- We are now using djb2xor instead of sha256 to hash puzzle answers
-- Lots of work on the built-in theme
+- Answer hashes are now the first 4 characters of the hex-encoded SHA1 digest
+- Reworked the built-in theme
 - [moth.mjs](theme/moth.mjs) is now the standard MOTH library for ECMAScript
 - Devel mode no longer accepts an empty team ID
 
diff --git a/pkg/transpile/puzzle.go b/pkg/transpile/puzzle.go
index e4045ce..23d8a90 100644
--- a/pkg/transpile/puzzle.go
+++ b/pkg/transpile/puzzle.go
@@ -4,7 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"context"
-	"crypto/sha256"
+	"crypto/sha1"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -85,9 +85,9 @@ func (puzzle *Puzzle) computeAnswerHashes() {
 	}
 	puzzle.AnswerHashes = make([]string, len(puzzle.Answers))
 	for i, answer := range puzzle.Answers {
-		sum := sha256.Sum256([]byte(answer))
+		sum := sha1.Sum([]byte(answer))
 		hexsum := fmt.Sprintf("%x", sum)
-		puzzle.AnswerHashes[i] = hexsum
+		puzzle.AnswerHashes[i] = hexsum[:4]
 	}
 }
 
diff --git a/pkg/transpile/puzzle_test.go b/pkg/transpile/puzzle_test.go
index 47db867..d6b9022 100644
--- a/pkg/transpile/puzzle_test.go
+++ b/pkg/transpile/puzzle_test.go
@@ -23,6 +23,12 @@ func TestPuzzle(t *testing.T) {
 		if (len(p.Answers) == 0) || (p.Answers[0] != "YAML answer") {
 			t.Error("Answers are wrong", p.Answers)
 		}
+		if len(p.Answers) != len(p.AnswerHashes) {
+			t.Error("Answer hashes length does not match answers length")
+		}
+		if len(p.AnswerHashes[0]) != 4 {
+			t.Error("Answer hash is wrong length")
+		}
 		if (len(p.Authors) != 3) || (p.Authors[1] != "Buster") {
 			t.Error("Authors are wrong", p.Authors)
 		}