What is the use of the signextend opcode?SIGNEXTEND performs the necessary sign extension when working with two's complement encoded signed integers in EVM. This allows operations on the values to produce the expected results for both positive and negative numbers. when there are negative numbers in calldata it cost more gas because the minor encoding, checking, arithmetic and comparison differences for negative numbers are why they cost slightly more gas than equivalent positive values. The EVM optimizes for the common case of non-negatives. why an int256 variable that stores -1 look like in hex?-1 stored as an int256 in Ethereum would be represented by the full 256-bit hex value ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff.

In binary, -1 is 1111111111111111111111111111111111111111111111111111111111111111

Converting that binary value to hex, we get:
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
Why is it important to ECDSA sign a hash rather than an arbitrary bytes32? hashing first before signing provides critical security properties like preimage resistance, binding signatures to data, canonical encoding and data integrity that direct signing of arbitrary bytes lacks. It's an important step for ECDSA signatures to provide robust cryptographic protection.
@EthSecurity1