diff --git a/src/net/model/prekeys.rs b/src/net/model/prekeys.rs
index 92aabff..dd7715e 100644
--- a/src/net/model/prekeys.rs
+++ b/src/net/model/prekeys.rs
@@ -1,7 +1,7 @@
 #![allow(non_camel_case_types)]
 use std::collections::HashMap;
 
-use proteus::keys::PreKeyBundle;
+use proteus::keys::{IdentityKey, PreKeyBundle};
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
@@ -10,14 +10,49 @@ pub struct PreKeyMap {
     pub value: HashMap<Uuid, HashMap<String, Option<PreKey>>>
 }
 
+impl PreKeyMap {
+    pub fn new() -> PreKeyMap {
+        PreKeyMap {
+            value: HashMap::new()
+        }
+    }
+
+    pub fn get(&self, id: &Uuid) -> Option<&HashMap<String, Option<PreKey>>> {
+        self.value.get(id)
+    }
+}
+
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct PreKey {
     pub key: PreKeyBundle
 }
 
+impl PreKey {
+    pub fn last_resort(k: &IdentityKey) -> LastPreKey {
+        let pk = proteus::PreKey::last_resort();
+        LastPreKey(PreKey { key: PreKeyBundle::new(k.clone(), &pk) })
+    }
+
+    pub fn from_str(s: &str) -> Option<PreKey> {
+        base64::decode(s).ok().and_then(|xs| {
+              PreKeyBundle::deserialise(xs.as_slice()).ok().map(|k| PreKey { key: k })
+          })
+    }
+}
+
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct LastPreKey(PreKey);
 
+impl LastPreKey {
+     pub fn new(p: PreKey) -> Option<LastPreKey> {
+         if p.key.prekey_id == proteus::MAX_PREKEY_ID {
+             Some(LastPreKey(p))
+         } else {
+             None
+         }
+    }
+}
+
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct ClientPreKey {
     pub id: String,