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This question already has an answer here:
In ECDSA, both signature(r,s) and (r,-s) are valid. However, in Bitcoin, it seems that the signature fails to be verified when s-part in the signature is bigger than half of the group order from this post https://bitcoin.stackexchange.com/questions/85946/low-s-value-in-bitcoin-signature I am wondering that if Ethereum is the same as Bitcoin. If yes, what is the reason that s needs to be a low-value?
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Ethereum has had this requirement since the homestead hard fork. This requirement was introduced as part of EIP-2 (see point 2 of https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.md#specification)
Rather than me repeat what others have already answered, here is an answer which explains concisely why the low s requirement is needed: https://bitcoin.stackexchange.com/a/38253
