In the first place, LL(1) parser for BER/DER is mostly trivial exercise, although somewhat tedious. Problem with ASN.1 is not with the specification itself but

In the first place, LL(1) parser for BER/DER is mostly trivial exercise, although somewhat tedious. Problem with ASN.1 is not with the specification itself but mostly in the fact that many people want to parse BER/DER with code that directly populates some application-specific data structure and depends on ASN.1 syntax of what they expect to parse. With that you invariably get very complex interface between parser library and application where both components have to handle various special cases correctly (to the point that the whole thing is not even leaky abstraction, because it almost isn't abstraction at all).