The file formats and naming convention of extensions is all over the place.
PEM (Privacy Enhanced Mail) Format
The most common format that CAs issue certificates in. The extension can be,
- crt
- cer
- cert
- pem
- key
The file is also Base64 encoded ASCII and with general certificates contains "----BEGIN CERTIFICATE---" and "---END CERTIFICATE----". The following certificates can be stored as PEM,
- Server Certificates (this the CA signed public key certificate)
- Intermediate Certificates
- Private Keys
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The BonsaiFramework uses the extension format.crt for the following certificates because the extension is recognized by Windows. Double-clicking on a crt file in Windows will show details about the certificate. We use the format.crt extension for the following,
By convention and because these keys do not work in Windows we use the following extensions, |
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DER Format
The DER format is a binary form of the certificate. It is best to use the.key der extension but sometimes the .cer extension is used. In that case you must open the with a text editor and look for BEGIN/END statements.
All types of certificates and private keys can be encoded in DR. DER is typically used with Java.
P7b Format
Converting from Open SSL to IKeyman
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See what is in a cert - http://www.sslshopper.com/certificate-decoder.html
A great decoder that shows encryption and key size along with the certificate information - https://certlogik.com/decoder/