I take it that Liquid is a side chain that is attached to the Bitcoin Blockchain (like in Lightning network)?
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Yes, Liquid is a sidechain to Bitcoin. Lightning is *not* a side-chain, but a 2nd layer on bitcoin, meaning that Lightning txs are Bitcoin txs that are simply held until needed, or until obsoleted by updated versions.
Ah, when I had a quick read, it seems they created a switch from Mimble Wimble (isn't it MW?) to El GAMAL commitment scheme because
1- MW is perfectly hiding but not perfectly binding (binds value to its commitment)
2-For the case of Quantum Computers threat, El GAMAL scheme although will be broken will protect against supply inflation
(I don't understand this part about inflation, would be grateful if u can explain it if u understand it)
No, MWEB uses Pedersen commitments, not El-Gamal ones. Their MW implementation differs from a pure MW one (such as Grin) in using a hybrid scheme to support non-interactive txs.
This hybrid scheme adds a receiver stealth address to every Pedersen commitment (whose blinding factor is also known to the sender) so that only the receiver can spend it.