Before a message is sent over a network, the message is encoded such that the receiver can understand the message. OpenSSL supports the following file formats for encoding keys, certificates, and digitally signed files:

• Distinguished Encoding Rules (DER) - Used for storing Abstract Syntax Notation One (ASN.1) structures containing keys and certificates.
• Privacy Enhanced Mail (PEM) - Used to store keys, certificates, and encrypted files.
• Public-Key Cryptography Standard 7 (PKCS#7) - Used to store digitally signed files.
• Public-Key Cryptography Standard 8 (PKCS#8) - Used to store private keys.
• Public-Key Cryptography Standard 12 (PKCS#12) - Used by browsers to store keys and certificates.