DKIM: move ed25519_privkey_pem_to_pubkey_raw_b64 to src/util/ and add usage notes...

[exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 67ade7b04a524af83adc05111aa3f4482ede5cd8..726f3af8a2268034f80c7e9c9a11ae83c1f24639 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -38946,6 +38946,20 @@ As they are a recent development, users should consider dual-signing
 for some transition period.
 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
 for EC keys.
+
+As of writing, producing EC key materials is not well supported
+by the major libraries.  GnuTLS 3.6.0 can create a private key:
+.code
+certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
+.endd
+
+To help in producing the required public key value for a DNS record
+the release package &_util/_& directory contains source for a utility
+buildable with GnuTLS 3.6.0;
+use it like this:
+.code
+ed25519_privkey_pem_to_pubkey_raw_b64 dkim_ed25519.private
+.endd
 .wen
 
 .option dkim_hash smtp string&!! sha256