Comment by zzo38computer

That is a text format, although DER is a binary format and encodes the data which there is represented by text. I think they should not have made a bit string (or octet string) to encapsulate another ASN.1 data and would be better to put it directly, but nevertheless it can work. The actual data to be parsed will be binary, not the text format like that.

DER is a more restricted variant of BER and I think DER is better than BER. PEM is also DER format but is encoded as base64 and has a header to indicate what type of data is being stored, rather than directly.