diff --git a/src/process.rs b/src/process.rs
index ff70c51..15bb27f 100644
--- a/src/process.rs
+++ b/src/process.rs
@@ -24,11 +24,20 @@ pub struct ProcessState {
 }
 
 impl ProcessState {
-    pub fn decrypt_pcd(&self) -> Value {
-        // TODO add real error management
+    pub fn decrypt_pcd(&self) -> anyhow::Result<Value> {
         let mut fields2plain = Map::new();
-        let _ = self.encrypted_pcd.decrypt_fields(&self.keys, &mut fields2plain);
-        Value::Object(fields2plain)
+        let fields2commit = self.pcd_commitment.to_value_object()?;
+        self.encrypted_pcd.decrypt_fields(&fields2commit, &self.keys, &mut fields2plain)?;
+        Ok(Value::Object(fields2plain))
+    }
+
+    pub fn get_message_hash(&self, approval: bool) -> anyhow::Result<AnkHash> {
+        let merkle_root = <Value as Pcd>::create_merkle_tree(&self.pcd_commitment)?.root().unwrap();
+        if approval {
+            Ok(AnkHash::ValidationYes(AnkValidationYesHash::from_byte_array(merkle_root)))
+        } else {
+            Ok(AnkHash::ValidationNo(AnkValidationNoHash::from_byte_array(merkle_root)))
+        }
     }
 
     fn list_modified_fields(&self, previous_state: Option<&ProcessState>) -> Vec<String> {