I've finally solved a strange OpenID "Bad signature" error on my web, which is using PHP OpenID library by JanRain... Some time ago I realized my OpenID-enabled web starts to reports "Bad signature" error during authentification process. I've found some tips (bad GMP etc.), but it don't help. Moreover, this error appears only with some IDs, like MyOpenID. Other providers, such as ClaimID, was OK. - Martin Maly