fix(whitepaper): biscuit_ct destructuring is destructuring a concatenation

papers/whitepaper.md

@@ -492,7 +492,7 @@ Note that the `mix(biscuit_ct)` call updates the chaining key, but that update d
 fn load_biscuit(biscuit_ct) {
     // Decrypt the biscuit
     let k = biscuit_key;
-    let (n, ct) = biscuit_ct;
+    let concat(n, ct) = biscuit_ct;
     let ad = lhash(
       "biscuit additional data",
       spkr, sidi, sidr);
@@ -957,6 +957,25 @@ Changes, in particular:
 17. Consistent naming convention. Always use the term `secret key`, never  `private key`.
 18. `pidiC` -> `pidi_ct`; to make it clearer that this is a cipher text
 19. Where we refer to the biscuit ciphertext, we now use the term `biscuit_ct`. Previously we had used various variable names such as `nct` (nonce followed by cipher text) or just plain `biscuit`.
+20. In `load_biscuit`, we make it clear that destructuring of `biscuit_ct` destructures a concatenation.
+
+    ``` {=tex}
+    \begin{quote}
+        \begin{minted}{pseudorust}
+        let (n, ct) = biscuit_ct;
+        \end{minted}
+    \end{quote}
+    ```
+
+    with
+
+    ``` {=tex}
+    \begin{quote}
+        \begin{minted}{pseudorust}
+        let concat(n, ct) = biscuit_ct;
+        \end{minted}
+    \end{quote}
+    ```
 
 #### 2025-06-24 – Specifying the `osk` used for WireGuard as a protocol extension
 

rosenpass/src/protocol/protocol.rs

@@ -3612,7 +3612,7 @@ impl CryptoServer {
                 self.pidm(peer.get(self).protocol_version.keyed_hash())?
                     .as_ref(),
             )?;
-            TV::check_value(&test_values.init_hello_pidic, &ih.pidic);
+            TV::check_value(&test_values.init_hello_pidi_ct, &ih.pidi_ct);
             TV::check_value(
                 &test_values.init_handshake_mix_3,
                 &hs.core.ck.clone().danger_into_secret(),

rosenpass/src/protocol/test_vector_sets.rs

@@ -61,10 +61,10 @@ pub struct HandleInitiationTestValues {
     #[test_vec(name = "hs.core.ck 2")]
     pub init_handshake_mix_2: TestValue<Secret<KEY_LEN>>,
 
-    #[test_vec(name = "ih.pidic")]
+    #[test_vec(name = "ih.pidi_ct")]
     #[test_vec(serialize_with = "serialize_byte_arr")]
     #[test_vec(deserialize_with = "deserialize_byte_arr")]
-    pub init_hello_pidic: TestValue<[u8; rosenpass_ciphers::Aead::TAG_LEN + 32]>,
+    pub init_hello_pidi_ct: TestValue<[u8; rosenpass_ciphers::Aead::TAG_LEN + 32]>,
 
     #[test_vec(name = "hs.core.ck 3")]
     pub init_handshake_mix_3: TestValue<Secret<KEY_LEN>>,