Can the ECDSA still work without present of hashing function? According to walkthrough steps for ECDSA topic from wikipedia as shown below, What if the impact if we don't apply the hashing function (highlighted in blue in the image) to the raw messages?
Although this sounds a bit silly, but let's say we have both with or without SHA256 engine test cases like below.
Hex Message (256 bits):
&quot;0123456789012345678901234567890123456789012345678901234567890123&quot;
Hex Message after SHA256 (256 bits):
&quot;9674d9e078535b7cec43284387a6ee39956188e735a85452b0050b55341cda56&quot;
Can anyone explain what is the problems with the first Hex Message if I proceed with this to the subsequent ECDSA signing flow?
Just assume Alice signed the raw message in this case?
The truthful answer here is that I don't know. I am pretty sure actually that the better answer is that this is unknown.  The assumption that the hash is only required for collision resistance is blatantly false, since typically one needs a random oracle for such schemes. In ECDSA specifically, we don't have actually have proof of security even with a random oracle, so it's even worse. However, given that it's been around for so many years, its security is essentially a well accepted assumption. However, as soon as you change something, and not hashing the message is certainly changing something, then it falls apart.