diff --git a/src/digest_engine.rs b/src/digest_engine.rs
index d7d3695..0644b41 100644
--- a/src/digest_engine.rs
+++ b/src/digest_engine.rs
@@ -1,6 +1,5 @@
-use anyhow::{anyhow, Context, Result};
+use anyhow::{anyhow, Result};
 use std::io;
-use std::io::{Read, Write};
 
 use log::*;
 
@@ -37,23 +36,9 @@ pub trait DigestEngine {
     fn update(&mut self, data: &[u8]);
 }
 
-// Dummy writer that implements Write for the none digest engine
-struct DummyWriter;
-
-impl DummyWriter {
-    fn new() -> Self {
-        DummyWriter
-    }
-}
-
-impl Write for DummyWriter {
-    fn write(&mut self, _buf: &[u8]) -> io::Result<usize> {
-        Ok(0)
-    }
-
-    fn flush(&mut self) -> io::Result<()> {
-        Ok(())
-    }
+// Writer that implements Write for the program digest engine
+struct ProgramWriter {
+    stdin: std::process::ChildStdin,
 }
 
 lazy_static! {
diff --git a/src/digest_engine/none.rs b/src/digest_engine/none.rs
index ba9599a..a454954 100644
--- a/src/digest_engine/none.rs
+++ b/src/digest_engine/none.rs
@@ -1,6 +1,6 @@
 use anyhow::Result;
 use crate::digest_engine::DigestEngine;
-use std::io::{Read, Write};
+use std::io::Write;
 use std::io;
 
 #[derive(Debug, Eq, PartialEq, Clone, Default)]
diff --git a/src/digest_engine/program.rs b/src/digest_engine/program.rs
index d6b3b2f..53530b2 100644
--- a/src/digest_engine/program.rs
+++ b/src/digest_engine/program.rs
@@ -1,10 +1,10 @@
-use anyhow::{anyhow, Context, Result};
+use anyhow::{anyhow, Result};
 use log::*;
 use std::env;
 use std::fs;
 use std::fs::File;
 use std::io;
-use std::io::{Read, Write};
+use std::io::Write;
 use std::os::unix::fs::PermissionsExt;
 use std::path::PathBuf;
 use std::process::{Command, Stdio};
@@ -70,7 +70,7 @@ impl DigestEngine for DigestEngineProgram {
         Ok("program".to_string())
     }
     
-    fn update(&mut self, data: &[u8]) {
+    fn update(&mut self, _data: &[u8]) {
         // This is handled by the ProgramWriter implementation
     }
 }
diff --git a/src/digest_engine/sha2.rs b/src/digest_engine/sha2.rs
index a70b1ad..fe78754 100644
--- a/src/digest_engine/sha2.rs
+++ b/src/digest_engine/sha2.rs
@@ -1,8 +1,6 @@
 use anyhow::Result;
 use log::*;
-use std::fs::File;
-use std::io::{Read, Write};
-use std::path::PathBuf;
+use std::io::Write;
 use sha2::{Digest, Sha256};
 use std::io;