feat: update -> finalize

src/lib.rs

@@ -226,6 +226,11 @@ pub trait Signable {
     fn verify(&mut self, pub_key: &ExtendedPoint) -> Result<(), OperationError>;
 }
 
+pub trait UpdateFinalize {
+    fn update(&mut self, write_data: &[u8]);
+    fn finalize(self, output_length: &u64) -> Result<Box<Vec<u8>>, OperationError>;
+}
+
 const RATE_IN_BYTES: usize = 136; // SHA3-256 r = 1088 / 8 = 136
 
 #[cfg(test)]

src/ops.rs

@@ -19,7 +19,7 @@ use crate::{
     },
     AesEncryptable, BitLength, Capacity, Hashable, KeyEncryptable, KeyPair, Message,
     OperationError, OutputLength, Rate, SecParam, Signable, Signature, SpongeEncryptable,
-    RATE_IN_BYTES,
+    UpdateFinalize, RATE_IN_BYTES,
 };
 use rayon::prelude::*;
 use tiny_ed448_goldilocks::curve::{extended_edwards::ExtendedPoint, field::scalar::Scalar};
@@ -883,10 +883,62 @@ impl AesEncryptable for Message {
     }
 }
 
+impl UpdateFinalize for Message {
+    /// Returns nothing and simply appends the write data into self.data
+    fn update(&mut self, write_data: &[u8]) {
+        self.msg.append(&mut write_data.to_owned());
+    }
+    /// Used in a sliding window
+    /// Internally, this calls cshake, then
+    /// passes self.data and returns the result
+    ///
+    fn finalize(self, output_length: &u64) -> Result<Box<Vec<u8>>, OperationError> {
+        if let Some(d) = self.d {
+            match cshake(&self.msg, *output_length, "", "", &d) {
+                Ok(new_msg) => {
+                    self.msg = Box::new(new_msg);
+                    Ok(self.msg)
+                }
+            },
+            Err(_) => {
+                Err(OperationError::CShakeError)
+            }
+        } else {
+            Err(OperationError::SecurityParameterNotSet)
+        }
+    }
+}
 ///
 /// TESTS
 ///
 #[cfg(test)]
+mod message_tests {
+    use crate::{ops::cshake, Message, SecParam::D256, UpdateFinalize};
+
+    #[test]
+    #[allow(non_snake_case)]
+    fn test_UpdateFinalize_initial_message() {
+        let mut m = Message::new("Initial data".as_bytes().to_vec());
+        m.d = Some(D256);
+        m.update("More data".as_bytes());
+        m.update("Even more data".as_bytes());
+
+        let expected_hash_result = cshake(
+            "Initial dataMore dataEven more data".as_bytes(),
+            256,
+            "",
+            "",
+            &D256,
+        );
+
+        assert_eq!(
+            m.finalize(),
+            expected_hash_result,
+            " The computed hash does not match the expected hash"
+        );
+    }
+}
+#[cfg(test)]
 mod cshake_tests {
     use crate::{ops::cshake, SecParam, NIST_DATA_SPONGE_INIT};