Very strange problem here: openssl successfully creates signatures but only those created as root are valid whereas created by another user (www-data) are invalid! All files are readable and there are not error messages:

# echo -ne Test | openssl dgst -ecdsa-with-SHA1 -sign activation.key > /tmp/asRoot.der
# su www-data
$ echo -ne Test | openssl dgst -ecdsa-with-SHA1 -sign activation.key > /tmp/asWww-data.der
$ uname -a
Linux linux 2.6.32-5-openvz-amd64 #1 SMP Mon Feb 25 01:16:25 UTC 2013 i686 GNU/Linux
$ cat /etc/debian_version
6.0.7

Both files (asRoot.der and asWww-data.der) are transfered to a different computer for verification with the public key:

$ echo -ne Test | openssl dgst -verify activation.pub -keyform DER -signature asRoot.der
Verified OK
$ echo -ne Test | openssl dgst -verify activation.pub -keyform DER -signature asWww-data.der
Verification Failure

That can't be true! What's wrong here?