Summary

The encoding of the algorithm identifier in JDK should omit the parameters field in AlgorithmIdentifier for the key agreement algorithms: X25519 and X448, and for the ECDSA signature algorithm: using SHA-224, SHA-256, SHA-384, or SHA-512.

Problem

For the X25519, X448, or ECDSA algorithm, JDK encodes its parameters field as NULL (containing two bytes for null-tag and length) in AlgorithmIdentifier. When the getEncoded() method is called by applications to obtain the key in its encoding format, the returned encoded data contains extra bytes for the parameters field.

Solution

RFC 8410 [1] and RFC 5758 [2] state that the parameters fields in AlgorithmIdentifier for the X25519, X448, and ECDSA algorithms should be absent. To have a conforming implementation, the encoding in JDK needs to omit the parameters field for those algorithms.

Specification

No changes to the JDK specification.

RFC for the AlgorithmIdentifier can be located at:

1. RFC 8410 [1]: Algorithm Identifiers for Ed25519, Ed448, X25519, and X448 for Use in the Internet X.509 Public Key Infrastructure
2. RFC 5758 [2]: Internet X.509 Public Key Infrastructure: Additional Algorithms and Identifiers for DSA and ECDSA

[1] https://tools.ietf.org/html/rfc8410#section-3

[2] https://tools.ietf.org/html/rfc5758#section-3.2