## Cryptography Basics

## EXAMPLE:

Modern cryptography concerns itself with the following four objectives:

1. Confidentiality

2. Integrity

3. Non-repudiation

4. Authentication

1. Confidentiality

2. Integrity

3. Non-repudiation

4. Authentication

## Types of Cryptography

Types of Cryptography

There are several ways to categorize encryption, but for our purposes here, I have broken them down into four main areas.

- Symmetric Encryption
- Asymmetric Encryption
- Hashes
- Wireless

## Symmetric Cryptography

Some of the common symmetric algorithms that you should be familiar with are:

· **DES** –

This was one of the original and oldest encryption schemes developed by IBM. It was found to be flawed and breakable and was used in the original hashing system of LANMAN hashes in early (pre-2000) Windows systems.

· **3DES** –

This encryption algorithm was developed in response to the flaws in DES. 3DES applies the DES algorithm three times (hence the name “triple DES”) making it slightly more secure than DES.

· **AES** –

This is the acronym for Secure Hash Algorithm. SHA algorithms are used to generate condensed representations of a message (message digest). It has various versions such as;

· **SHA-0**:

produces 120-bit hash values. It was withdrawn from use due to significant flaws and replaced by SHA-1.

· **SHA-1**:

produces 160-bit hash values. It is similar to earlier versions of MD5. It has cryptographic weakness and is not recommended for use since the year 2010.

· **SHA-2**:

It has two hash functions namely SHA-256 and SHA-512. SHA-256 uses 32-bit words while SHA-512 uses 64-bit words.

· **SHA-3**:

This algorithm was formally known as Keccak.

· **RC4** –

This is a streaming (it encrypts each bit or byte rather than a block of information) cipher and developed by Ronald Rivest of RSA fame. Used in VoIP and WEP.

**Blowfish** –

The first of Bruce Schneier‘s encryption algorithms. It uses a variable key length and is very secure. It is not patented, so anyone can use it without license.

## Asymmetric Cryptography

Asymmetric cryptography uses different keys on both end of the communication channel. This cryptography is very slow, about 1,000 times slower than symmetric cryptography, so we don’t want to use it for bulk encryption or streaming communication. It does, however, solve the key exchange problem. Since we don’t need to have the same key on both ends of a communication, we don’t have the issue of key exchange.

Some of common asymmetric encryption schemes you should be

familiar with are:

**Diffie-Hellman** – Many people in the field of cryptography regard the

Diffie-Hellman key exchange to be the greatest development in cryptography Without going deep into the mathematics, Diffie and

Hellman developed a way to generate keys without having to exchange the keys,

thereby solving the key exchange problem that plagues symmetric key encryption.

**RSA** – Rivest, Shamir, and Adleman is a scheme of asymmetric encryption that uses factorization of very large prime numbers as the relationship between the two keys.

**PKI** – Public key infrastructure is the widely used asymmetric system for exchanging confidential information using a private key and a public key.

**ECC** – Elliptical curve cryptography is becoming

increasing popular in mobile computing as it efficient, requiring less

computing power and energy consumption for the same level of security. ECC

relies upon the shared relationship of two functions being on the same

elliptical curve.

**PGP** – Pretty Good Privacy uses asymmetric encryption to assure the privacy and integrity of

email messages.

## Hashes

Hashes are one-way encryption. A message or password is encrypted in a way that it cannot be reversed or unencrypted. You might wonder, “What good would it do us to have a something encrypted and then not be able to decrypt it?” Good question!

Some of the very popular

hashes are:

**MD4**

**MD4**

This was an early hash by Ron Rivest and haslargely been discontinued in use due to collisions.

**MD5**

**MD5**

The most widely used hashing system. It’s 128-bit

and produces a 32-character message digest.

**SHA1**

**SHA1**

Developed by the NSA, it is more secure than MD5, but

not as widely used. It has 160-bit digest which is usually rendered in

40-character hexadecimal. Often used for certificate exchanges in SSL, but

because of recently discovered flaws, is being deprecated for that purpose.

## Wireless Cryptography

Wireless cryptography has been a favorite of Hackers as so many here are

trying to crack wireless access points. As you might guess, wireless cryptography is symmetric (for speed), and as with all symmetric cryptography,

key exchange is critical.

#### · **WEP**

This was the original encryption scheme for wireless and was quickly discovered to be flawed. It used RC4, but because of the small key size (24-bit), it repeated the IV about every 5,000 packets enabling easy cracking on a busy network.

#### · **WPA**

This was a quick fix for the flaws of WEP, adding a larger key and TKIP to make it

slightly more difficult to crack.

**· WPA2-PSK**

This was the first of the more secure wireless encryption schemes. It uses a pre-shared

key and AES. It then salts the hashes with the AP name or SSID. The hash is exchanged at authentication in a four-way handshake between the client and AP.

**· WPA2-Enterprise**

This wireless encryption is the most secure. It uses a 128-bit key, AES, and a remote authentication server (RADIUS).

I hope you keep coming back, as we continue to explore

the wonderful world of information security and hacking!