the process of secret (crypto=secret or
hidden, graph=write or draw, both in Greek) writing
cryptanalysis
the process of trying to extract a secret that
has been hidden by some cryptographic technique
cryptology
the study of cryptography and cryptanalysis
(logos in Greek is word, thought, reason, or study)
plaintext or cleartext
the message which we wish to
send in a secure way
to encrypt
to apply a cryptographic technique to a plaintext,
in order to get a new version called the
ciphertext
the message after it has been encrypted, so its
secrets are hidden and it can be safely transmitted through insecure
channels, after which the recipient wants
to decrypt
to apply the opposite of the encryption technique,
so as to extract the original plaintext
key
a small piece of secret information which can be used as
part of the encryption and decryption process applied to any message
code
an approach to encryption where words or phrases of the
plaintext are simply replaced with fixed other words, phrases or symbols
looked up (in a codebook)
cipher
an approach to encryption where the ciphertext
is created by applying some algorithm to the individual symbols (letters) of
the plaintext
transposition cipher
a cipher in which the letters of the
plaintext are simply rearanged
substitution cipher
a cipher in which the letters of the
plaintext are sequentially replaced by other letters (or numbers or symbols)
brute force or exhaustive search
a cryptanalytic
technique whereby one looks for a "reasonable" decryption as one tries
all keys in the
keyspace
the set of all possible keys for some cryptographic
technique
man-in-the-middle attack
an approach to breaking the security
of encrypted communications where the attacker (usually called Eve)
intercepts all messages between the parties who wish to communicate (usually
called Alice and Bob) and re-writing all of their messages
symmetric [secret-key] cryptography
a cryptographic
technique where the encryption and decryption algorithms use the same key
asymmetric [public-key] cryptography
a cryptographic technique
where the encryption and decryption algorithms use two different keys, and
knowing one of the keys does not help much in finding the other key; these
two keys are called the public key and private key
digital signature
a piece of data which is attached to an
electronic message which proves that the author of that particular message
possesses a particular private key (called the signing key)
digital certificate
a digital signature on a message which
states that a certain entity on the Internet is who they claim to be, where
the signing key is one owned by a recognized central authority, called
the Certificate Authority or CA