diff --git a/src/sshutil.rs b/src/sshutil.rs
index 149adb0..5e6d7bc 100644
--- a/src/sshutil.rs
+++ b/src/sshutil.rs
@@ -7,14 +7,13 @@ pub fn with_sign(mut vec: Vec<u8>) -> Vec<u8> {
 
 pub fn generate_ssh_string(e: &[u8], n: &[u8], comment: &str) -> String {
     let mut ssh_key = vec![];
-    let ssh_rsa_bytes = "ssh-rsa".as_bytes();
-    ssh_key.extend_from_slice(&(ssh_rsa_bytes.len() as u32).to_be_bytes()[..]);
-    ssh_key.extend_from_slice(ssh_rsa_bytes);
-    let e = with_sign(e.to_vec());
-    ssh_key.extend_from_slice(&(e.len() as u32).to_be_bytes()[..]);
-    ssh_key.extend_from_slice(&e);
-    let n = with_sign(n.to_vec());
-    ssh_key.extend_from_slice(&(n.len() as u32).to_be_bytes()[..]);
-    ssh_key.extend_from_slice(&n);
+    append_slice_with_len(&mut ssh_key, "ssh-rsa".as_bytes());
+    append_slice_with_len(&mut ssh_key, &with_sign(e.to_vec()));
+    append_slice_with_len(&mut ssh_key, &with_sign(n.to_vec()));
     format!("ssh-rsa {} {}", base64::encode(&ssh_key), comment)
+}
+
+pub fn append_slice_with_len(v: &mut Vec<u8>, s: &[u8]) {
+    v.extend_from_slice(&(s.len() as u32).to_be_bytes()[..]);
+    v.extend_from_slice(s);
 }
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