Key Elements of Cryptographic Systems
Key elements of cryptographic systems include:
• Encryption algorithm—Mathematically based function or calculation that encrypts or decrypts data.
• Encryption key—Piece of information similar to a password that makes the encryption or decryption process
unique. A user needs the correct key to access or decipher a message, as the wrong key converts the message into an
unreadable form.
• Key length—Predetermined length for the key. The longer the key, the more difficult it is to compromise in a brute
force attack where all possible key combinations are tried.
Effective cryptographic systems depend upon a variety of factors including:
• Algorithm strength
• Secrecy and difficulty of compromising a key
• Nonexistence of back doors by which an encrypted file can be decrypted without knowing the key
• Inability to decrypt parts of a ciphertext message and prevent known plaintext attacks
• Properties of the plaintext known by a perpetrator
Key Systems
There are two types of cryptographic systems:
• Symmetric Key Systems—These use single, secret, bidirectional keys that encrypt and decrypt.
• Asymmetric Key Systems—These use pairs of unidirectional, complementary keys that only encrypt or decrypt.
Typically, one of these keys is secret, and the other is publicly known.
Public key systems are asymmetric cryptographic systems. Most encrypted transactions over the Internet use a
combination of private/public keys, secret keys, hash functions (fixed values derived mathematically from a text
message) and digital certificates (that prove ownership of a public encryption key) to achieve confidentiality,
message integrity, authentication and nonrepudiation by either sender or recipient (also known as a public
key infrastructure [PKI]). Essentially, keys and hash values are used to transform a string of characters into a shorter
or fixed-length value or key that represents the original string. This encryption process allows data to be stored and
transported with reduced exposure so data remains secure as it moves across the Internet or other networks.