public final class Asn1

The DER this package reads and writes: a reader over definite-length encodings and the handful of writers the formats here need.

BER’s indefinite lengths are refused. X.509, PKCS#10 and the PKCS#12 files OpenSSL and the JDK write are DER; a file that is not is reported as such rather than half read.

It is public for formats this package does not cover – a CMS SignedData structure, an Apple receipt, an attestation extension – so they are read with the same bounds checks rather than by hand.

Asn1.Reader outer = new Asn1.Reader(der).open(Asn1.SEQUENCE);
String type = outer.oid();
byte[] content = outer.open(Asn1.explicit(0)).raw(Asn1.SEQUENCE);