Sharing the Master Keys in BIP32 What is the Best way to share the Master Public Key and Master Chain code generated using BIP32 in Bicoins with a user that I don't trust ?

I just want the second user to monitor my wallet and not spend coins. What will be the best way to share my Master Keys ?
This depends on the wallet (keypath) you are using.

If your wallet is based on BIP44 (most wallets are), sharing the extended master public key will not allow the other party deriving pubkeys to monitor incoming funds (because of hardened key derivation). You need to share the specific account extended public key. Your fist account is at keypath m / 44' / 0' / 0', second at m / 44' / 0' / 1', etc.

Instead of sharing the pure pubkey together with the chaincode, we use "extended public keys". You can identify a such base58check encoded string by the first 4 chars "xpub".

As far as I know there are only a few wallets in the wilde who can do such exports/imports.