Can't export(and convert to plain) ed25519 keytype?

Vault
1

I’m newbie of vault and trying to export the ed25519 key(purpose is study)
update the exportable policy but can’t get plain text type
it is encode as base64

I’m follow this guide
(Transit - Secrets Engines - HTTP API | Vault | HashiCorp Developer)

  1. vault write transit/keys/{keyname}/config exportable=true

  2. get result as base64
    {“request_id”:“37b146d9-9ab2-4109-c2f7-a39177219717”,“lease_id”:“”,“renewable”:false,“lease_duration”:0,“data”:{“keys”:{“1”:“{base64data}”},“name”:“keyname”,“type”:“ed25519”},“wrap_info”:null,“warnings”:null,“auth”:null}

vault write transit/decrypt/{keyname} ciphertext=vault:v1:{base64data}

but got this result
Error writing data to transit/decrypt/keyname: Error making API request.

URL: PUT http://0.0.0.0:8200/v1/transit/decrypt/keyname

Code: 400. Errors:

  • message decryption not supported for key type ed25519

There are no way to convert?