@@ -139,6 +139,8 @@ func (c *InProcessSigner) GetSignedTimestamp(_ context.Context) (*string, []byte
 // directly can produce fewer than 96 bytes when r or s is small, which the
 // registry rejects with "invalid signature size for ECDSA P-384". FillBytes
 // left-pads each component to 48 bytes so verification always sees 96 bytes.
+// r and s come from ecdsa.Sign in this file and are bounded by the P-384 group
+// order, so they always fit in 48 bytes and FillBytes cannot panic.
 func encodeECDSAP384Signature(r, s *big.Int) []byte {
 	signature := make([]byte, 96)
 	r.FillBytes(signature[:48])