Is Encryption Speech?
                      A Cryptographer's Perspective

                           Dorothy E. Denning
                          Georgetown University
                                    
                            February 12, 1995



Encryption (also called cryptography) is a method of transforming
communications and stored data into a form that is unintelligible to
anyone other than the intended receiver.  The original data are
referred to as plaintext and the encrypted data as ciphertext.  With
modern encryption systems, the data are represented as streams of 0's
and 1's, and the encryption algorithm transforms the plaintext bit
stream into one that appears random.  The transformation is
parameterized by a secret key, which is also a random string of 0's and
1's, and the receiver must know this key in order to decrypt and
recover the original data.

This note considers the question of whether modern encryption is speech
or even a method or manner of speech, where the word "speech" is used
loosely to refer to all forms of expression, including oral
communications, written documents, and images.  I shall consider this
question from my perspective as a cryptographer.  I am neither a
Constitutional lawyer nor a linguist.

Speech in this loose sense is the communication or expression of human
thoughts and emotions, including requests, offers, assertions, beliefs,
declarations, concepts, moods, and feelings.  Communication occurs
through notations such as language, which often have both an oral form
(speech in the strict sense) and a written form.  A notational system
is a set of symbols and conventions used in a more or less uniform way
by a body of people.

By contrast, encryption is a method of concealing expression.  It
involves the transformation of data (which typically conveys some
expression) into a form (ciphertext) that by itself cannot be
understood.  The objective of encryption is not to communicate or even
to facilitate communications, but rather to hide one's communications.
To obtain the communications, the effect of the encryption must be
undone through decryption.  Encryption thus is a privacy enhancing
technology.

Encryption has been compared with using a foreign language.  But it is
nothing like a foreign language because there are no constructs for
expressing thoughts or emotions in ciphertext directly.  Instead, one
must express thoughts and emotions in some ordinary language and then
transform the communication into ciphertext through encryption.
Ciphertext is not an independent language for communication; indeed,
ciphertext does not even exist except as the result of encrypting a
particular message.  Encryption and decryption are not like
translations between English and French because there is no regard to
meaning or interpretation of the bits.  Encryption and decryption are
simply bit transformations that have the property of cancelling each
other.

Thus, it would appear that encryption is not speech, but rather the
antithesis of speech.  However, it may not be quite so simple since the
act of encrypting communicates something, namely that the sender has an
encryption product, is able to use it, and may have something worth
hiding.  Nevertheless, what can be communicated in this way is
extremely limited and not the same as what is communicated in the
message itself.

Encryption might be regarded as a method or mode of communication in
that data are being transmitted in encrypted form.  However, encryption
contributes nothing either to the act of expression or to data
transmission, which typically involves sending packets of bits through
a computer network or signals through the phone system.  Whether the
data are in plaintext or ciphertext is totally irrelevant to
transmission.  Encryption is not analogous to whispering, which is a
mode of oral communication that preserves the language while
simultaneously providing some privacy.

Encryption has been compared with using an envelope rather than a
postcard as a means of sending a message through the postal system.
However, an envelope is a physical entity that serves a purpose besides
concealment, namely as a container for packaging together multiple
sheets of paper (or other items) and for protecting papers from
damage.  It is a tool that aids communication.  It does not transform
the message that it carries.  Encryption, on the other hand, is not a
physical entity and does not aid communication in any manner.  It
transforms a message, but does not carry it.

My conclusion is that modern encryption is predominately a privacy
enhancing technology rather than speech.  Although encryption might be
regarded as a manner of speech, it is unlike other methods in that it
contributes nothing to communication.

One implication of this interpretation is that regulation of encryption
would not violate the First Amendment.  Another is that restrictions on
the use of encryption could not be used as a basis for prohibiting the
use of an obscure foreign language or any other ordinary language.