SideChain is not same as AltCoins
-> SideChain does not require POW nor "blockchain" to work .. (but SC can use them, it is problem of SC-participants)
this is not true. everyone has been talking about how to secure a SC blockchain with the most common solution and criticism being merge mining.
Believe me, It is SC-participant's problem "how to secure SC". They can use blockchain, POW, POS, central entity, 10 oracles, signatures of all participants ... possibilities are endless. -> Bitcoin users not affected (there can be 1,000,000,000 sidechains -> not affecting Bitcoin)
1) SC will only set-up some address/addresses in Bitcoin-world (lock bitcoins to prevent double-spent) -> and create SideChain-world
SC world need security or else attackers will steal the scBTC
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SC-world can work under the radar, no one know if SC exists. It depends what they use (blockchain, POW, POS, DPOS, central entity, 10 oracles, ..). They can know each others ... they can use tor to exchange transactions
2) In SC-world you can do SC-transactions (even by e-mail) -> build some hash-tree (you do not have to broadcast transactions to ALL WORLD and verify that ALL SEE THEM, b/c only participants matters)
3) SC-world has rules (Bitcoin users not affected) how to withdrawn/unlock bitcoins from scBTC (they must be able to create valid bitcoin transaction to unlock bitcoins).
you still haven't answered how a SC can't hurt Bitcoin if the economic value of a scBTC starts exceeeding a BTC in USD terms b/c of a significant innovation.
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