Certificate FormatsOnline version Security + certificate formats by Brody Campbell 1 PEM 2 P7B 3 CER 4 DER 5 P12PFX Extensions: .pem .cer .crt .key Format: CER or DER Server cert, cert chain, keys, CRL Purpose: Almost any cert purpose Common Extensions: .p7b / .p7c Format: DER Common Use: To share public key Can contain: certs, cert chains, CRL, NEVER private key Common Extensions: .cer Format: Binary Purpose: Binary certs Common Extensions: .der Format: ASCII Purpose: ASCII certs Common Extensions: .p12 / .pfx Format: Binary (CER) Common Purpose: Used to store private keys with certificate Can contain: certs, cert chains, private keys Used on Windows Systems