application/pkcs8

A private key in the format modern tooling agrees on: PKCS #8 wraps the key material with an algorithm identifier, so one structure carries RSA, EC or Ed25519 alike. The type means the raw DER binary; the same data usually travels PEM-armored between BEGIN PRIVATE KEY lines, which is a different serialization even though tools read both. This is the one payload whose leak is a full compromise — and note the sibling application/pkcs8-encrypted for keys wrapped under a passphrase.

Defined by RFC 5958 · IANA registration. Registry facts from the IANA media-types registry via mime-db.