From b165323185ed05a9fad46ff94ef319b4a18762fe Mon Sep 17 00:00:00 2001
From: Azer Sadykhzadeh <azer.piano14@gmail.com>
Date: Sat, 17 Oct 2026 09:03:56 +0000
Subject: [PATCH] Compute the vault KDF's four lanes in parallel

Argon2 was built without its parallel feature, so unlock ran all four
lanes one after another on a single thread.
---
 Cargo.lock | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml |  6 +++++-
 2 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index 33c749f3..6cda9f3b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -114,6 +114,7 @@ dependencies = [
  "blake2",
  "cpufeatures 0.3.1",
  "password-hash",
+ "rayon",
 ]
 
 [[package]]
@@ -858,6 +859,25 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "622f3fc73690be383c7214310406f28a90e6edeadc3cea882f9d71e495b9711a"
+dependencies = [
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc74980687109a3b14c72fd458107bf0baa1da1a1a805e178d15501ba9b86d9d"
+dependencies = [
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "crossbeam-utils"
 version = "0.8.23"
@@ -1352,6 +1372,12 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "either"
+version = "1.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0e9c71c2167ca323c882b99918929403426e2373ea17242ff5653e0d5e1058be"
+
 [[package]]
 name = "elliptic-curve"
 version = "0.14.1"
@@ -4070,6 +4096,26 @@ version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "20675572f6f24e9e76ef639bc5552774ed45f1c30e2951e1e99c59888861c539"
 
+[[package]]
+name = "rayon"
+version = "1.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fb39b166781f92d482534ef4b4b1b2568f42613b53e5b6c160e24cfbfa30926d"
+dependencies = [
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22e18b0f0062d30d4230b2e85ff77fdfe4326feb054b9783a3460d8435c8ab91"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.5.18"
diff --git a/Cargo.toml b/Cargo.toml
index d8e63d11..b076444f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -38,7 +38,11 @@ thiserror = "2"
 tracing = "0.1"
 tracing-subscriber = "0.3"
 zeroize = { version = "1", features = ["derive"] }
-argon2 = "0.6"
+# `parallel` computes Argon2's lanes on separate threads (rayon). The vault's
+# KDF uses four lanes, so unlock waits for roughly a quarter of the work on a
+# machine with four or more cores; the result and its cost to an attacker are
+# unchanged.
+argon2 = { version = "0.6", features = ["parallel"] }
 aes-gcm = "0.11"
 uuid = { version = "1", features = ["v4", "serde"] }