A valid digital signature gives a recipient reason to believe that the message was created by a known sender (authentication), that the sender cannot deny having sent the message (non-repudiation), and that the message was not altered in transit (integrity).
Load index is an assigned number that corresponds with the load-carrying capacity of a tire. Most passenger car tire load indexes range from 75 to 100, but a few carry more. You'll also find the maximum load elsewhere on the tire sidewall, both in lbs and kg.
A tire with the correct tire load index for your vehicle assures you that your tires are made to handle the weight of your vehicle. The speed rating shows the maximum speed your tires can handle, which tends to be more important in countries with roadways that are not subject to speed limitations.