diff --git a/src/crypto/util.rs b/src/crypto/util.rs
index cff4a8e..87c2ba6 100644
--- a/src/crypto/util.rs
+++ b/src/crypto/util.rs
@@ -1,7 +1,7 @@
 use crate::error::{Result, Error};
 use simple_error::simple_error;
-use block_modes::block_padding::{ZeroPadding, Padding};
 
+/// Extracts the the last `n` bytes of a slice. n being the blocksize.
 pub fn extract_last_block(data: &[u8], blocksize: usize) -> Result<&[u8]> {
     if data.len() % blocksize != 0 {
         return Err(simple_error!("Data is not compatible with blocksize: data(length): {}, blocksize: {}.", data.len(), blocksize).into())
@@ -10,11 +10,15 @@ pub fn extract_last_block(data: &[u8], blocksize: usize) -> Result<&[u8]> {
     Ok(&data[(data.len() - blocksize)..])
 }
 
-pub fn expand_to_blocksize(data: &mut [u8], blocksize: usize) -> Result<&mut [u8]> {
-    // let diff = data.len() % blocksize;
+/// Takes a given input and zero pads it to a multiple of blocksize
+pub fn expand_to_blocksize(data: &mut [u8], blocksize: usize) -> Result<Vec<u8>> {
+    let diff = data.len() % blocksize;
 
-    match ZeroPadding::pad(data, data.len(), blocksize) {
-        Ok(x) => {Ok(x)}
-        Err(e) => {Err(Error::PadError(e))}
+    if diff == 0 {
+        return Ok(data.to_vec());
+    } else {
+        let mut buf = vec![0 as u8; data.len() + blocksize - diff];
+        buf[..data.len()].copy_from_slice(data);
+        Ok(buf)
     }
 }
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