Derive the name segment directly from the key

wnfs-wg · Jun 30, 2023 · 122fa2a · 122fa2a
1 parent 76627f1
commit 122fa2a
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Showing 2 changed files with 16 additions and 16 deletions.
diff --git a/wnfs/src/private/node/header.rs b/wnfs/src/private/node/header.rs
@@ -1,4 +1,4 @@
-use super::{PrivateNodeHeaderSerializable, TemporalKey};
+use super::{PrivateNodeHeaderSerializable, TemporalKey, REVISION_SEGMENT_DSS};
 use crate::{error::FsError, private::RevisionRef};
 use anyhow::{bail, Result};
 use libipld_core::cid::Cid;
@@ -130,6 +130,11 @@ impl PrivateNodeHeader {
         TemporalKey::from(&self.ratchet)
     }
 
+    pub(crate) fn derive_revision_segment(&self) -> NameSegment {
+        let hasher = self.ratchet.derive_key(REVISION_SEGMENT_DSS);
+        NameSegment::from_digest(hasher)
+    }
+
     /// Gets the revision name for this node.
     ///
     /// It's this node's name with a last segment added that's
@@ -159,7 +164,7 @@ impl PrivateNodeHeader {
     /// ```
     pub fn get_revision_name(&self) -> Name {
         self.name
-            .with_segments_added(Some(self.derive_temporal_key().to_revision_segment()))
+            .with_segments_added(Some(self.derive_revision_segment()))
     }
 
     /// Gets the name for this node.

diff --git a/wnfs/src/private/node/keys.rs b/wnfs/src/private/node/keys.rs
@@ -14,7 +14,6 @@ use sha3::{Digest, Sha3_256};
 use skip_ratchet::Ratchet;
 use std::fmt::Debug;
 use wnfs_hamt::Hasher;
-use wnfs_nameaccumulator::NameSegment;
 
 //--------------------------------------------------------------------------------------------------
 // Type Definitions
@@ -32,8 +31,14 @@ pub struct TemporalKey(pub AesKey);
 // Constants
 //--------------------------------------------------------------------------------------------------
 
-const REVISION_SEGMENT_DOMAIN_SEPARATION_STRING: &str = "wnfs/segment deriv from temporal";
-const TEMPORAL_KEY_DOMAIN_SEPARATION_STRING: &str = "wnfs/temporal deriv from ratchet";
+/// The revision segment derivation domain separation string
+/// used for salting the hashing function when turning
+/// node names into revisioned node names.
+pub(crate) const REVISION_SEGMENT_DSS: &str = "wnfs/segment deriv from temporal";
+/// The temporal key derivation domain seperation string
+/// used for salting the hashing function when deriving
+/// symmetric keys from ratchets.
+pub(crate) const TEMPORAL_KEY_DSS: &str = "wnfs/temporal deriv from ratchet";
 
 //--------------------------------------------------------------------------------------------------
 // Implementations
@@ -70,13 +75,6 @@ impl TemporalKey {
             .unwrap_with_padding_vec(ciphertext)
             .map_err(|e| AesError::UnableToEncrypt(format!("{e}")))?)
     }
-
-    pub(crate) fn to_revision_segment(&self) -> NameSegment {
-        let mut hasher = Sha3_256::new();
-        hasher.update(REVISION_SEGMENT_DOMAIN_SEPARATION_STRING);
-        hasher.update(self.0.as_bytes());
-        NameSegment::from_digest(hasher)
-    }
 }
 
 impl SnapshotKey {
@@ -186,10 +184,7 @@ impl From<[u8; KEY_BYTE_SIZE]> for TemporalKey {
 impl From<&Ratchet> for TemporalKey {
     fn from(ratchet: &Ratchet) -> Self {
         Self::from(AesKey::new(
-            ratchet
-                .derive_key(TEMPORAL_KEY_DOMAIN_SEPARATION_STRING)
-                .finalize()
-                .into(),
+            ratchet.derive_key(TEMPORAL_KEY_DSS).finalize().into(),
         ))
     }
 }