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Security Fundamentals & Crypto · Intermediate

Distinguished Encoding Rules (DER)

Binary encoding format for X.509 certificates and keys.

Definition

DER is the binary form of ASN.1-encoded certificates, common in Windows and Java environments. It typically uses .der or .cer extensions. PEM is simply DER data Base64 encoded with header lines.

Example

Windows certificate export offers 'DER encoded binary X.509 (.CER)' as an option.

Exam tip

Know DER = binary and PEM = Base64 of the same data.

Related terms