| 1 | // SPDX-License-Identifier: AGPL-3.0-or-later |
| 2 | |
| 3 | package sealbox |
| 4 | |
| 5 | import ( |
| 6 | "golang.org/x/crypto/curve25519" |
| 7 | ) |
| 8 | |
| 9 | // derivePublic computes the X25519 public key from a 32-byte private |
| 10 | // key. NaCl's box package doesn't expose this directly when loading a |
| 11 | // pre-existing private key (only `GenerateKey` returns both halves); |
| 12 | // we use curve25519.X25519 against the basepoint to derive. |
| 13 | func derivePublic(pub, priv *[32]byte) error { |
| 14 | out, err := curve25519.X25519(priv[:], curve25519.Basepoint) |
| 15 | if err != nil { |
| 16 | return err |
| 17 | } |
| 18 | copy(pub[:], out) |
| 19 | return nil |
| 20 | } |
| 21 |