chore: clean .gitignore cache

backend/internal/util/crypto.go

@@ -1,42 +0,0 @@
-package util
-
-import (
-	"crypto/subtle"
-)
-
-// ConstantTimeCompare compares two strings in constant time to prevent comparison timing attacks.
-//
-// PROTECTION SCOPE:
-// This function protects against timing attacks during the comparison operation itself,
-// where an attacker might measure how long it takes to compare two strings byte-by-byte
-// to infer information about the expected value.
-//
-// IMPORTANT LIMITATIONS:
-// This does NOT protect against timing variance in database queries. If you retrieve a token
-// from the database (e.g., WHERE invite_token = ?), the DB query timing will vary based on
-// whether the token exists, potentially revealing information to an attacker through timing analysis.
-// See backend/internal/api/handlers/user_handler.go for examples of this limitation.
-//
-// DEFENSE-IN-DEPTH:
-// Despite this limitation, using constant-time comparison is still valuable as part of a
-// defense-in-depth strategy. It eliminates one potential timing leak and should be used
-// when comparing sensitive values like API keys, tokens, or passwords that are already
-// in memory.
-//
-// Returns true if the strings are equal, false otherwise.
-func ConstantTimeCompare(a, b string) bool {
-	aBytes := []byte(a)
-	bBytes := []byte(b)
-
-	// subtle.ConstantTimeCompare returns 1 if equal, 0 if not
-	return subtle.ConstantTimeCompare(aBytes, bBytes) == 1
-}
-
-// ConstantTimeCompareBytes compares two byte slices in constant time to prevent comparison timing attacks.
-//
-// This function has the same protection scope and limitations as ConstantTimeCompare.
-// See ConstantTimeCompare documentation for details on what this protects against and
-// what it does NOT protect against (e.g., database query timing variance).
-func ConstantTimeCompareBytes(a, b []byte) bool {
-	return subtle.ConstantTimeCompare(a, b) == 1
-}