Fix GrindKey() key derivation in Go implementation#106
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GrindKey() diverged from the reference grind_key (paradex-py / paradex.js) in several ways, producing keys that did not match other SDKs: 1. Inverted range check (issue tradeparadex#102): the loop used `< 0`, looping while the key was already in range and accepting out-of-range keys. Rejection sampling requires grinding *while* the key is out of range, so the condition is now `>= 0`. 2. SHA256_EC_MAX_DIGEST was built from a string literal containing spaces, which big.Int.SetString rejects (ok=false) while the unchecked return left the value at 0. That 0 silently masked bug tradeparadex#1 (a hash is never < 0, so the loop never ran) and would have caused an infinite loop once the condition was flipped. Compute 2^256 directly instead. 3. The index was hex-encoded with `%02x`, which stops keeping the length even past 255 (e.g. 256 -> "100" vs the reference "0100"). Pad to an even number of hex digits, matching padded_hex. 4. The seed was not padded to even length, so an odd-length seed panicked in hex.DecodeString. Pad it the same way. Add utils_test.go pinning GrindKey output to golden values generated from the paradex-py reference, plus range and hex-prefix checks. Fixes tradeparadex#102
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Summary
GrindKey()in the Go sample diverged from the referencegrind_key(paradex-py / paradex.js), so it produced Stark private keys that did not match the other SDKs for the same Ethereum signature. This fixes the divergence (closes #102) and adds tests pinning the output to reference values.Bugs fixed
Inverted range check ([BUG] - GrindKey() in Go Implementation #102). The grind loop used
key.Cmp(maxAllowedVal) < 0, looping while the key was already in range and accepting out-of-range keys. Rejection sampling requires grinding while the key is out of range, so the condition is now>= 0.SHA256_EC_MAX_DIGESTwas silently zero. It was parsed from a string literal containing spaces, whichbig.Int.SetStringrejects (ok=false); the unchecked return left the value at0. That0masked bug Add example for Paradex onboarding and authentication #1 (a hash is never< 0, so the buggy loop never ran) and would have turned into an infinite loop once the condition was flipped. It is now computed directly as2^256viaLsh.Index hex padding. The index was encoded with
%02x, which only guarantees even length up to 255 (e.g.256 -> "100"vs the reference"0100"). It is now padded to an even number of hex digits, matchingpadded_hex.Seed hex padding. The seed was not padded to even length, so an odd-length seed panicked in
hex.DecodeString. It is padded the same way.Tests
Adds
go/utils_test.gowith golden values generated from the paradex-py reference (grind_key), plus range and0x-prefix checks. Verified the tests fail against the previous behavior and pass with this fix.Fixes #102