Add hash personalization traits

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>

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;