DER encoded certificate
From Just Solve the File Format Problem
DER encoded certificate is a file format for storing an X.509 certificate.
It is one type of DER file. DER is a subset of BER format. BER is a serialization format for the abstract ASN.1 format.
Examples
To display the contents of a DER encoded certificate using OpenSSL:
openssl x509 -noout -text -inform der -in example.der
To convert from DER encoded certificate format to PEM encoded certificate format:
openssl x509 -in example.der -inform der -outform pem -out example.pem
