Change seed for retransmit to use blob signature (#4727)

* Switch seed for retransmit to use blob signature

* Use seed_len

* Use last bytes of signature as seed instead of first bytes

core/src/packet.rs

@@ -406,8 +406,9 @@ impl Blob {
 
     pub fn seed(&self) -> [u8; 32] {
         let mut seed = [0; 32];
-        seed[0..8].copy_from_slice(&self.index().to_le_bytes());
-        seed[8..16].copy_from_slice(&self.slot().to_le_bytes());
+        let seed_len = seed.len();
+        let signature_bytes = self.get_signature_bytes();
+        seed[0..seed_len].copy_from_slice(&signature_bytes[(signature_bytes.len() - seed_len)..]);
         seed
     }
 
@@ -488,6 +489,10 @@ impl Blob {
         self.set_data_size(new_size as u64);
     }
 
+    pub fn get_signature_bytes(&self) -> &[u8] {
+        &self.data[SIGNATURE_RANGE]
+    }
+
     pub fn store_packets<T: Borrow<Packet>>(&mut self, packets: &[T]) -> u64 {
         let size = self.size();
         let mut cursor = Cursor::new(&mut self.data_mut()[size..]);
@@ -609,7 +614,7 @@ impl Signable for Blob {
     }
 
     fn get_signature(&self) -> Signature {
-        Signature::new(&self.data[SIGNATURE_RANGE])
+        Signature::new(self.get_signature_bytes())
     }
 
     fn set_signature(&mut self, signature: Signature) {