Cybersecurity - Encryption Fundamentals

Encryption Fundamentals

Encryption is the process of converting a plaintext message into a secure-coded form of text, called ciphertext. The ciphertext cannot be understood without converting back, via decryption—the reverse process—to plaintext. This is done via a mathematical function and a special encryption/decryption password called the key. In many countries, encryption is subject to governmental laws and regulations that limit the key size or define what may not be encrypted.

Encryption is part of a broader science of secret languages called cryptography, which is generally used to:

• Protect information stored on computers from unauthorized viewing and manipulation

• Protect data in transit over networks from unauthorized interception and manipulation

• Deter and detect accidental or intentional alterations of data

• Verify authenticity of a transaction or document

Encryption is limited in that it cannot prevent the loss of data. It is possible to compromise encryption programs if encryption keys are not protected adequately. Therefore, encryption should be regarded as an essential, but incomplete, form of access control that should be incorporated into an organization’s overall computer security program.

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.