$ caff -u E358BEFB 40AD1FA6
[INFO] Importing key 7258EBFBE358BEFB from your normal GnuPGHome.
[INFO] fetching keys, this will take a while...
[NOTICE] Import failed for: 40AD1FA6.
Some keys could not be imported - continue anyway? [y/N] y
[WARN] Assuming 40AD1FA6 is a fine keyid.
[INFO] Sign the following keys according to your policy, then exit gpg with 'save' after signing each key
gpg --local-user E358BEFB --homedir=/home/user/.caff/gnupghome --secret-keyring /home/userfaith/.gnupg/secring.gpg --no-aut
o-check-trustdb --trust-model=always --edit 40AD1FA6 sign
gpg: 警告: homedir 「/home/user/.caff/gnupghome」の安全でない許可gpg (GnuPG) 1.4.9; Copyright (C) 2008 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

No public keys found with list-key 40AD1FA6 (note that caff uses its own keyring in /home/user/.caff/gnupghome).

下記の対処[debian-users:52995]で解決。
>> gpg: 警告: homedir 「/home/user/.caff/gnupghome」の安全でない許可
>
>は /home/user/.caff/gnupghome のパーミッションが readable by >others
>になっているために起きる警告なので、
>
>chmod 700 ~/.caff/gnupghome
>
>すると良いと思います。

以下は古い記述
caffのホームディレクトリ宛に鍵束のファイルを読み込んだところ、解決
$ gpg --homedir /home/user/.caff/gnupghome --import ksp-200909.gpg
(中略)
gpg: 処理数の合計: 26
gpg: 読込み: 25 (RSA: 23)
gpg: 変更なし: 1
gpg: 絶対的に信用する鍵が見つかりません
$ caff -u E358BEFB 40AD1FA6
[INFO] Importing key 7258EBFBE358BEFB from your normal GnuPGHome.
[INFO] fetching keys, this will take a while...
[NOTICE] Import failed for: 40AD1FA6.
Some keys could not be imported - continue anyway? [y/N] y
[WARN] Assuming 40AD1FA6 is a fine keyid.
[INFO] Sign the following keys according to your policy, then exit gpg with 'save' after signing each key
gpg --local-user E358BEFB --homedir=/home/user/.caff/gnupghome --secret-keyring /home/user/.gnupg/secring.gpg --no-aut
o-check-trustdb --trust-model=always --edit 40AD1FA6 sign
gpg: 警告: homedir 「/home/user/.caff/gnupghome」の安全でない許可gpg (GnuPG) 1.4.9; Copyright (C) 2008 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

pub 4096R/40AD1FA6 作成: 2009-06-25 満了: 無期限 利用法: SC
sub 4096R/35468237 作成: 2009-06-25 満了: 無期限 利用法: E
(中略)
本当に全ユーザーIDに署名しますか? (y/N) y

pub 4096R/40AD1FA6 作成: 2009-06-25 満了: 無期限 利用法: SC
  主鍵の指紋: 5E62 9EE5 2321 9735 7B84 CF43 3224 7FBB 40AD 1FA6

(中略)
Mail signature for hoge [Y/n] Y
(略)
$