In this digital era we are living, a reliable means of digital identification is becoming more and more necessary.
Digital certification is a process which permits that two people determine the identity of each other using only digital data (i.e., without using paper IDs) and over a computer network (i.e., there is no need for the people to face each other physically).
To read more about Digital Certification, check out these pages by Wikipedia, Microsoft and Verisign.
Brazil is one of the countries in the world where digital identification has advanced most.
And besides identity, the Brazilian method permits also check out validity of signature and integrity of documents.
Much of the advance in Brazil is explained by the fact that the Government is directly involved in the process.
Brazil is one of the few countries in the World (if not the only one) where the State enacted a law providing for an official Public Key Infrastructure; read the full text (with comments) of the Law creating the official PKI in Brazil.