diff --git a/libimagref/src/hasher.rs b/libimagref/src/hasher.rs
new file mode 100644
index 00000000..b2970837
--- /dev/null
+++ b/libimagref/src/hasher.rs
@@ -0,0 +1,48 @@
+use std::path::PathBuf;
+use std::io::Read;
+
+use error::RefErrorKind as REK;
+use error::MapErrInto;
+
+use crypto::sha1::Sha1;
+use crypto::digest::Digest;
+
+use result::Result;
+
+/// The Hasher trait is used to implement custom hashing functions for the ref library.
+/// This means that one can define how the hash of a reference is constructed from the content of
+/// the file to ref to.
+pub trait Hasher {
+
+    fn hash_name(&self) -> &'static str;
+    fn create_hash<R: Read>(&mut self, pb: &PathBuf, contents: &mut R) -> Result<String>;
+
+}
+
+pub struct DefaultHasher {
+    hasher: Sha1,
+}
+
+impl DefaultHasher {
+
+    pub fn new() -> DefaultHasher {
+        DefaultHasher { hasher: Sha1::new() }
+    }
+
+}
+
+impl Hasher for DefaultHasher {
+
+    fn hash_name(&self) -> &'static str {
+        "default"
+    }
+
+    fn create_hash<R: Read>(&mut self, _: &PathBuf, contents: &mut R) -> Result<String> {
+        let mut s = String::new();
+        try!(contents.read_to_string(&mut s).map_err_into(REK::IOError));
+        self.hasher.input_str(&s[..]);
+        Ok(self.hasher.result_str())
+    }
+
+}
+
diff --git a/libimagref/src/lib.rs b/libimagref/src/lib.rs
index eac8842c..79be27bd 100644
--- a/libimagref/src/lib.rs
+++ b/libimagref/src/lib.rs
@@ -29,6 +29,7 @@ module_entry_path_mod!("ref", "0.2.0");
 
 pub mod error;
 pub mod flags;
+pub mod hasher;
 pub mod lister;
 pub mod reference;
 pub mod result;
diff --git a/libimagref/src/reference.rs b/libimagref/src/reference.rs
index 6e38aa50..9dc96e00 100644
--- a/libimagref/src/reference.rs
+++ b/libimagref/src/reference.rs
@@ -518,11 +518,3 @@ impl<'a> Into<FileLockEntry<'a>> for Ref<'a> {
 
 }
 
-fn hash_file_contents(f: &mut File) -> String {
-    let mut hasher = Sha1::new();
-    let mut s = String::new();
-    f.read_to_string(&mut s);
-    hasher.input_str(&s[..]);
-    hasher.result_str()
-}
-