From 0e16ed1a4319203d5907661c6bc7bf334b77faee Mon Sep 17 00:00:00 2001
From: Sylvain Pelissier <sylvain.pelissier@gmail.com>
Date: Mon, 17 Jul 2023 13:01:39 +0200
Subject: [PATCH] Add hash personalization traits

---
 digest/src/core_api/wrapper.rs | 18 +++++++++++++++++-
 digest/src/lib.rs              | 15 +++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/digest/src/core_api/wrapper.rs b/digest/src/core_api/wrapper.rs
index af77b11c8..342cb90b2 100644
--- a/digest/src/core_api/wrapper.rs
+++ b/digest/src/core_api/wrapper.rs
@@ -3,7 +3,8 @@ use super::{
     Reset, UpdateCore, XofReaderCoreWrapper,
 };
 use crate::{
-    ExtendableOutput, ExtendableOutputReset, FixedOutput, FixedOutputReset, HashMarker, Update,
+    ExtendableOutput, ExtendableOutputReset, FixedOutput, FixedOutputReset, HashMarker,
+    PersonalizationInit, Update,
 };
 use block_buffer::BlockBuffer;
 use core::fmt;
@@ -184,6 +185,21 @@ where
     }
 }
 
+impl<T> PersonalizationInit for CoreWrapper<T>
+where
+    T: BufferKindUser + PersonalizationInit,
+{
+    type PersonalizationExtArg = T::PersonalizationExtArg;
+    #[inline]
+    fn new(personalization: &[u8]) -> Self {
+        Self::from_core(T::new(personalization))
+    }
+
+    fn new_ext(personalization_ext: &Self::PersonalizationExtArg) -> Self {
+        Self::from_core(T::new_ext(personalization_ext))
+    }
+}
+
 #[cfg(feature = "oid")]
 #[cfg_attr(docsrs, doc(cfg(feature = "oid")))]
 impl<T> AssociatedOid for CoreWrapper<T>
diff --git a/digest/src/lib.rs b/digest/src/lib.rs
index 04ea98931..3bfcff684 100644
--- a/digest/src/lib.rs
+++ b/digest/src/lib.rs
@@ -273,6 +273,21 @@ pub trait VariableOutputReset: VariableOutput + Reset {
     }
 }
 
+/// Trait for hash functions with personalization string for domain separation.
+pub trait PersonalizationInit: Sized {
+    // It would be nice to define a default value equal to `[u8]`, but unfortunately
+    // associated type defaults are currently unstable
+
+    /// Extended personalization
+    type PersonalizationExtArg;
+
+    /// Create new hasher instance with the given personalization string.
+    fn new(personalization: &[u8]) -> Self;
+
+    /// Create new hasher instance with the given extended personalization.
+    fn new_ext(personalization_ext: &Self::PersonalizationExtArg) -> Self;
+}
+
 /// The error type used in variable hash traits.
 #[derive(Clone, Copy, Debug, Default)]
 pub struct InvalidOutputSize;