Add nonce information

docs/protocol/transaction-anatomy.md

@@ -21,12 +21,20 @@ In addition, a transaction has the following fields to ensure its integrity and
 Users create transactions and sign them with their private keys. Then, the **transaction and its signature** are broadcast together to the network, where they are validated and processed.
 
 :::tip
-Each transaction has exactly one `Signer` and `Receiver`, but can have multiple `Actions`
+Each transaction has exactly one `Signer` and `Receiver`, but can have multiple `Actions`.
+:::
+
+:::info About nonce values
+- When adding a key, the `nonce` is automatically assigned - particularly, it is given the value `block height * 10^6` - so the value in the `ADD_KEY` action is ignored
+- A transaction is accepted only if the `nonce` value is in the range of:
+  - `[(current_nonce_of_access_key + 1) .. (block_height * 10^6)]`
+- Once a transaction is accepted, the access key's `nonce` is set to the `nonce` value of the included transaction
 :::
 
 ---
 
 ## Actions
+
 Each transaction can have **one or multiple** `Actions`, which are the actual operations to be performed on the `Receiver` account. There are 9 types of actions that can be performed:
 
 1. `FunctionCall`: to invoke a function on a contract (optionally attaching NEAR to the call)

docs/protocol/transaction-execution.md

@@ -27,7 +27,7 @@ While creating the `Receipt`, the `signer` gets $NEAR deducted from its balance
 If the `signer` and `receiver` coincide - e.g. the `signer` is adding a Key - the `Receipt` is immediately processed in this first block and the transaction is considered final.
 
 #### Block #2: The Receipt is Processed
-If the `signer` and `receiver` differs - e.g. the `signer` transfers NEAR to the `receiver` - the `Receipt` is processed in a second block. 
+If the `signer` and `receiver` differs - e.g. the `signer` transfers NEAR to the `receiver` - the `Receipt` is processed in a second block.
 
 During this process a `FunctionCall` could span a **cross-contract call**, creating one or multiple new `Receipts`.
 
@@ -114,3 +114,15 @@ See the examples below for more details.
 :::tip
 You can check the status of a transaction using the [NearBlocks explorer](https://nearblocks.io/)
 :::
+
+---
+
+## Nonce values
+
+The `nonce` is a number that is incremented for each transaction sent by the transaction's `Signer`.
+On a valid transaction, the `nonce` value should follow these rules:
+
+- When adding a key, the `nonce` is automatically assigned - particularly, it is given the value `block height * 10^6` - so the value in the `ADD_KEY` action is ignored
+- A transaction is accepted only if the `nonce` value is in the range of:
+  - `[(current_nonce_of_access_key + 1) .. (block_height * 10^6)]`
+- Once a transaction is accepted, the access key's `nonce` is set to the `nonce` value of the included transaction