rust-protocol: Fix checksum.

common/rust-protocol/src/lib.rs

         if !self.encode(&mut data[8..30]) {
             return false;
         }
-        let checksum = State::<KERMIT>::calculate(&data[0..30]);
+        let checksum = State::<KERMIT>::calculate(&data[8..30]);
         data[30..].copy_from_slice(&checksum.to_le_bytes());
         encrypt_cbc(key, data);
         true