In an X.509 certificate, the serial number is encoded as the ASN.1 integer type, which is arbitrary length. So that can't map to a native integer type on any platform.
I'd chalk this up to the author of the relevant module not really grokking the two's complement behavior in java.math.BigInteger.
I'd chalk this up to the author of the relevant module not really grokking the two's complement behavior in java.math.BigInteger.