The

usdsi.com

website is no longer available.
The website of US Data Security Inc. operated from 1998 to 2009. The company was active in the field of Public Key Cryptography and established the "US Data Security Public-Key Challenge", a contest on a new method of Public key encryption called the TTM (Tame Transformation Method).

Public-key cryptography, also known as asymmetric cryptography, is a class of cryptographic algorithms which requires two separate keys, one of which is secret and one of which is public. Although different, the two parts of this pair are mathematically linked. The public key is used to encrypt plaintext or to verify a digital signature and the private key is used to decrypt ciphertext or to create a digital signature. The term 'asymmetric' is derived from the use of different keys to perform these opposite functions, each the inverse of the other as opposed with conventional ('symmetric') cryptography which relies on the same key to perform both.

For further information about Public Key Cryptography, please visit the Wikipedia article here.