I want to use storedsafe as a validation server using pam_yubico, according to verify.php the nonce parameter is required and to me it seems pam_yubico doesn't support that. See https://github.com/Yubico/yubico-pam/blob/master/README.
Do you have any suggestions?
Are you using a fairly new version of pam_yubico? I think the newer versions of yubico-pam is using libykclient (https://github.com/Yubico/yubico-c-client), which adds, and checks, the nonce parameter.