Fix wrong slice position resulting in cut plain text on decryption

package.json

@@ -1,7 +1,7 @@
 {
   "name": "ascon-js",
   "private": false,
-  "version": "1.0.2",
+  "version": "1.0.3",
   "author": "Simon Osterlehner <[email protected]>",
   "license": "MIT",
   "sideEffects": false,

src/ascon.spec.ts

@@ -9,6 +9,9 @@ const nonce = fromHex("6c27fff03b58975180cf12de2fd2d6e2");
 
 const arrayToLong = fromHex("01020304050607080900010203040506070809");
 const plainText = new TextEncoder().encode("ascon");
+const plainTextLonger = new TextEncoder().encode(
+  "This is a longer message used for testing purposes and is definitely longer than 32 bytes."
+);
 const associatedData = new TextEncoder().encode("ASCON");
 
 describe("Ascon.hash", () => {
@@ -201,3 +204,56 @@ describe("Ascon.decrypt", () => {
     ).toThrow("Could not be decrypted. Tags don't match.");
   });
 });
+
+describe("Ascon de- and encryption", () => {
+  it.each([
+    {
+      variant: "Ascon-128" as AsconEncryptionVariant,
+      associatedData,
+    },
+    {
+      variant: "Ascon-128" as AsconEncryptionVariant,
+      associatedData: undefined,
+    },
+    {
+      variant: "Ascon-128a" as AsconEncryptionVariant,
+      associatedData,
+    },
+    {
+      variant: "Ascon-128a" as AsconEncryptionVariant,
+      associatedData: undefined,
+    },
+    {
+      variant: "Ascon-80pq" as AsconEncryptionVariant,
+      associatedData,
+    },
+    {
+      variant: "Ascon-80pq" as AsconEncryptionVariant,
+      associatedData: undefined,
+    },
+  ])(
+    "Should correctly encrypt and decrypt different length plaintext with $variant",
+    ({ variant, associatedData }) => {
+      [Uint8Array.from([]), plainText, plainTextLonger].forEach((item) => {
+        const keyToUse = variant === "Ascon-80pq" ? key20 : key;
+        const encrypted = Ascon.encrypt(keyToUse, nonce, item, {
+          associatedData,
+          variant,
+        });
+
+        // Check the length of the encrypted text + 16 bytes for the tag
+        expect(encrypted).toHaveLength(item.length + 16);
+        expect(encrypted).not.toEqual(item);
+
+        const decrypted = Ascon.decrypt(keyToUse, nonce, encrypted, {
+          associatedData,
+          variant,
+        });
+
+        // Check the length of the encrypted text + 16 bytes for the tag
+        expect(decrypted).toHaveLength(item.length);
+        expect(decrypted).toEqual(item);
+      });
+    }
+  );
+});

src/ascon.ts

@@ -401,9 +401,11 @@ export class Ascon {
 
       plaintext = concatArrays(
         plaintext,
-        intToBytes(S[0] ^ c0, 8),
-        intToBytes(S[1] ^ c1, 8)
-      ).slice(0, cLastLen);
+        concatArrays(intToBytes(S[0] ^ c0, 8), intToBytes(S[1] ^ c1, 8)).slice(
+          0,
+          cLastLen
+        )
+      );
 
       if (cLastLen < 8) {
         S[0] = c0 ^ (S[0] & cMask) ^ cPadding;

src/main.ts

@@ -1,4 +1,5 @@
 import { Ascon, fromHex, randomBytes, toHex } from ".";
+import { arrayEquals } from "./helper";
 
 const main = () => {
   const key = fromHex("e4ea93530575bd6f5dc68cb241e32d1c");
@@ -7,7 +8,11 @@ const main = () => {
   const nonce = fromHex("6c27fff03b58975180cf12de2fd2d6e2");
   const associated = new TextEncoder().encode("ASCON");
 
-  const plaintext = new TextEncoder().encode("ascon");
+  const plaintext = new TextEncoder().encode(
+    "Hallo mein Name ist Simon Osterlehner und ich bin in Muenchen geboren."
+  );
+
+  console.log("Plaintext", plaintext);
 
   const encrypted = Ascon.encrypt(key, nonce, plaintext, {
     variant: "Ascon-128a",
@@ -25,7 +30,9 @@ const main = () => {
 
   const text = new TextDecoder().decode(decrypted);
 
-  console.log("Decrypted", text);
+  console.log("Decrypted", decrypted);
+
+  console.log("Decrypted", arrayEquals(decrypted, plaintext), text);
 };
 
 main();