much computation. However, mathematicians have been trying (for other reasons) to solve this

equation for a long time, and many believe there is no shortcut to a solution.

key, more computation is required to solve the equation, and hence the message is more secure.

is the basis of the Digital Signature Standard (DSS), a U.S. Government document. As with

other digital signature algorithms, DSA lets one person with a secret key “sign” a document, so

that others with a matching public key can verify it must have been signed only by the holder of

the secret key.

message. They are called “one-way” because there is no known way (without infeasible

amounts of computation) to find a message with a given hash value. In other words, a hash value

can be determined for a given message, but it is not known to be possible to construct

in symmetric key encryption, except that there is no decryption key: the operation is

irreversible. The result has a fixed length, which is 160 bits in the case of the Secure Hash

Algorithm (SHA) used by DSA.

themselves. Thus it is possible to sign a message’s hash value, without even knowing the

content of the message. This makes it possible to have

document existed (and was signed), without the notary knowing anything about what was in the

document.