Well-known security company RSA (named after the popular Rivest Shamir Adleman public key encryption algorithm on which it held the patents) provides SecurID authenticators in all three form factors.

The RSA algorithm is a feast of genius that combines theoretical math and practical coding into working asymmetric cryptography. Here’s how it works.

The RSA algorithm, in essence, allows a message to be encrypted without the sender knowing the key, says Lynn Batten, a mathematician and security researcher at Deakin University. Here's how it works.

To an outsider, the RSA algorithm appears like a card trick: You pick a card from a stack, hide it (this is like encryption), and after some manipulations the magician produces your card—bazinga!