Encryption is the conversion of data into a form, called
a ciphertext, that cannot be easily understood by unauthorized
people. Decryption is the process of converting encrypted
data back into its original form, so it can be understood.
The
use of encryption/decryption is as old as the art of communication.
In wartime, a cipher, often incorrectly called a "code,"
can be employed to keep the enemy from obtaining the contents
of transmissions. (Technically, a code is a means of representing
a signal without the intent of keeping it secret; examples
are Morse code and ASCII.) Simple ciphers include the substitution
of letters for numbers, the rotation of letters in the alphabet,
and the "scrambling" of voice signals by inverting
the sideband frequencies. More complex ciphers work according
to sophisticated computer algorithms that rearrange the
data bits in digital signals.
In
order to easily recover the contents of an encrypted signal,
the correct decryption key is required. The key is an algorithm
that "undoes" the work of the encryption algorithm.
Alternatively, a computer can be used in an attempt to "break"
the cipher. The more complex the encryption algorithm, the
more difficult it becomes to eavesdrop on the communications
without access to the key.
Encryption/decryption
is especially important in wireless communications. This
is because wireless circuits are easier to "tap"
than their hard-wired counterparts. Nevertheless, encryption/decryption
is a good idea when carrying out any kind of sensitive transaction,
such as a credit-card purchase online, or the discussion
of a company secret between different departments in the
organization. The stronger the cipher -- that is, the harder
it is for unauthorized people to break it -- the better,
in general. However, as the strength of encryption/decryption
increases, so does the cost.
In
recent years, a controversy has arisen over so-called strong
encryption. This refers to ciphers that are essentially
unbreakable without the decryption keys. While most companies
and their customers view it as a means of keeping secrets
and minimizing fraud, some governments view strong encryption
as a potential vehicle by which terrorists might evade authorities.
These governments, including that of the United States,
want to set up a key-escrow arrangement. This means everyone
who uses a cipher would be required to provide the government
with a copy of the key. Decryption keys would be stored
in a supposedly secure place, used only by authorities,
and used only if backed up by a court order. Opponents of
this scheme argue that criminals could hack into the key-escrow
database and illegally obtain, steal, or alter the keys.
Supporters claim that while this is a possibility, implementing
the key escrow scheme would be better than doing nothing
to prevent criminals from freely using encryption/decryption.
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