What is cryptography?
Cryptography is the science of mathematical security. On modern computers,
cryptography includes encryption, authentication, and integrity. A good
introduction to the
concepts can be found here:
http://www.webopedia.com/TERM/C/cryptography.html
What is symmetric cryptography?
Encryption uses a mathematical key to provide secrecy. Symmetric cryptography
refers to encryption systems that use the same key to encrypt and
decrypt. A longer explanation can be found here:
http://www.webopedia.com/TERM/S/symmetric_key_cryptography.htm
There are many books that explain these concepts in more detail.
We recommend Chapter XX of Secrets & Lies: Digital Security
in a Networked World, by Bruce Schneier.
What is public-key cryptography?
This is a modern form of cryptography, where a different key
is used for encryption and decryption. Many modern security
systems make extensive use
of public-key
cryptography. See:
http://www.webopedia.com/TERM/P/public_key_cryptography.html
Can there be unquestioned assurance that the key remains secret?
Of course not. Keys are either known by people, or stored in
devices that people have access to. No matter what protocols
and procedures are used,
people are
always prone to making mistakes The most we can do is minimize
our reliance on secrets and then build procedural safeguards around
the few secrets that
we depend
on people to keep.
How can voters be sure the key is kept secret?
They can’t. They have no choice but to trust those who have
access to the key.
How can cryptography be used to enhance voting technology
security?
Cryptography can be used for several purposes in voting
systems. It can be used to prevent eavesdropping, for
example, in
network links between the
computers
on which votes are cast and the central computers that
record those votes. Where Internet voting is used, cryptography
becomes an essential safeguard
to voter
privacy.
Cryptography can be used to authenticate voting data,
giving very high assurance that it really did come from
a particular
voting machine and has not been
tampered with in any way. This can be used to prevent
forgery of precinct voting records.
Software authentication can be used to prevent acceptance
and use of unauthorized voting system software.
Can encryption replace the need for paper records of
votes cast?
No. The security problems encryption solves are important,
but there are other voting security problems that encryption
does
not solve. For some more
information,
please see:
http://www.schneier.com/crypto-gram-0312.html#9
http://www.schneier.com/crypto-gram-0411.html#1
http://www.schneier.com/crypto-gram-0411.html#2
There are some very
ingenious proposals to use encryption in ways that permit a voter
to be assured that their
vote was
counted as intended without allowing
that voter to prove to anyone else how they voted.
Some of these schemes promise paperless elections. Other schemes
give the voter
a printed copy
of their encrypted
ballot, proving to the voter that this ballot
really does
indeed include their selections in the voting
booth, and then destroying
the proof before
the voter
walks away.
How can you ensure that cryptography is being
applied correctly?
One of the most difficult problems with cryptography
is that only a very small number of people
really understand today's
best cryptosystems. There
are more
people who understand how to correctly use
these systems but who do not necessarily understand
their underlying
mathematics, but even this group is relatively
small. Most people, therefore, are forced to
trust the words of the experts. See:
http://www.schneier.com/essay-028.html
Why isn’t keeping the security details
of voting systems a good idea?
The relationship of security and secrecy
is subtle, and counterintuitive. The idea
that secret equals secure is not true. For a longer explanation,
see:
http://www.schneier.com/crypto-gram-0205.html#1
More on the History of Cryptography
Where does the word cryptography come from?
The word "cryptography" is taken from the Greek word "kryptos" meaning
hidden and graphein meaning writing. Cryptography is the science
of hidden writing or more accurately the study of encrypting
or encyphering messages so that their content is obscured until
they are decrypted or decyphered. Typically, the encryption
process uses a key or password, the encryption key, and the message can
only be decrypted if the correct decryption key is given.
What is symmetric key encryption?
The oldest form of cryptography, dating back at least 2000 years,
uses the same key for encryption and decryption. With symmetric
key encryption, the sender and receiver of the message must
each keep the same key or password as a secret in order to guarantee
their privacy when they exchange encrypted messages.
Other Online Resources on Cryptography:
RSA's FAQ on Cryptography