From 3eb36433babee35b49c67bdf6c9f5e89539be890 Mon Sep 17 00:00:00 2001
From: krlosMata <krlosmata@gmail.com>
Date: Fri, 3 Sep 2021 16:11:51 +0200
Subject: [PATCH] add review comments

---
 docs/developers/sdk.md | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/docs/developers/sdk.md b/docs/developers/sdk.md
index 5593931..035a449 100644
--- a/docs/developers/sdk.md
+++ b/docs/developers/sdk.md
@@ -26,7 +26,7 @@ In this tutorial we will walk through the process of using the SDK to:
     - [Configure Hermez Environment](#configure-hermez-environment)
   - [Check token exists in Hermez Network](#check-token-exists-in-hermez-network)
   - [Create a Wallet](#create-a-wallet)
-    - [Derive private babyjubjub from ethereum account](#derive-private-babyjubjub-from-ethereum-account)
+    - [Derive private Babyjubjub from Ethereum account](#derive-private-babyjubjub-from-ethereum-account)
   - [Deposit Tokens from Ethereum into Hermez Network](#deposit-tokens-from-ethereum-into-hermez-network)
   - [Verify Balance](#verify-balance)
   - [Withdrawing](#withdrawing)
@@ -147,16 +147,26 @@ We can create a new Hermez wallet by providing the Ethereum private key of an Et
   const hermezEthereumAddress2 = wallet2.hermezEthereumAddress
 
 ```
-### Derive private babyjubjub from ethereum account
-The specification to derive private babyjubjub from ethereum account is the following:
+### Derive private Babyjubjub from Ethereum account
+The specification to derive private Babyjubjub from Ethereum account is the following:
 - Message to be signed: `Hermez Network account access.\n\nSign this message if you are in a trusted application only.`
-- Sign message with your ethereum private key: `signature = eth_sign(MESSAGE)`
+- Sign message with your Ethereum private key: `signature = eth_sign(MESSAGE)`
   - message string is parsed to bytes using utf8 conversion. Further details can be found [here](http://stackoverflow.com/questions/18729405/how-to-convert-utf8-string-to-byte-array) and [here](https://github.com/ethers-io/ethers.js/blob/ce8f1e4015c0f27bf178238770b1325136e3351a/packages/strings/src.ts/utf8.ts#L202)
   - please note that the json RPC method used is `eth_sign`. Further details can be found [here](`https://eth.wiki/json-rpc/API#eth_sign`)
-- The computed `signature` is then hashed using keccak256 hash to finally derive the babyjubjub private key: `privateKeyBabyjubjub = keccak256(signature)`
+- The computed `signature` is then hashed using keccak256 hash to finally derive the Babyjubjub private key: `privateKeyBabyjubjub = keccak256(signature)`
+
+> notes:
+> - if ecdsa standard libraries are used instead of Ethereum specific ones, remember to add 27 to `v` signature value
+> - The public Babyjubjub key is derived from the private Babyjubjub key. Hermez Network uses the public Babyjubjub key compressed form (uint256)
+> - There are two representations of public Babyjubjub key: hexadecimal and base64
+>   - Hexadecimal is done by converting the public Babyjubjub key compressed form (uint256) into big-endian hexadecimal string
+>   - Base64 is done by converting the public Babyjubjub key compressed form (uint256) into its little-endian base64 string
+>     - it also adds an additional checksum byte computed as the sum of all its bytes (mod $2^{8}$) which is concatenated at the end of the public Babyjubjub key compressed form
+
+> implementations examples can be found [here](https://github.com/hermeznetwork/hermezjs/blob/main/src/hermez-wallet.js#L33), [here](https://github.com/hermeznetwork/hermezjs/blob/main/src/addresses.js#L109) and [here](https://github.com/hermeznetwork/hermez-go-sdk/blob/main/account/creation.go#L115)
 
 ## Deposit Tokens from Ethereum into Hermez Network
-Creating a Hermez account and depositing tokens is done simultaneously as an L1 transaction.  In this example we are going to deposit 1 `ETH` tokens into the newly created Hermez accounts. 
+Creating a Hermez account and depositing tokens is done simultaneously as an L1 transaction.  In this example we are going to deposit 1 `ETH` token into the newly created Hermez accounts.
 
 ```js
   // set amount to deposit