TLS on Windows: Converting between PEM and DER File Formats for TLS

By default, OpenSSL files are created in Privacy Enhanced Mail (PEM) format. SSL files that are created in Windows operating environments are created in Distinguished Encoding Rules (DER) format.

Under Windows, you can import a file that is created in either PEM or DER format. However, a digital certificate that is created in DER format must be converted to PEM format before it can be included in a trust list on UNIX.

Here is an example of converting a server digital certificate from DER input format to PEM output format :

OpenSSL> x509 -inform DER -outform PEM -in server.der -out server.pem

Here is an example of converting a server digital certificate from PEM input format to DER output format:

OpenSSL> x509 -inform PEM -outform DER -in server.pem -out
server.der