Question

Identify and describe the three main types of cryptography. In your answer provide an example of how each of these three main types of cryptography is used in provide appropriate security in a technology solution.

Answer 1

The three main types of cryptography are :

1) Public Key Cryptography

Public Key Cryptography involves the use of one-way functions, which are mathematical functions that are computationally easy but their inverse functions are difficult to compute. The trick used in Public Key Cryptography is to find a trap in the one-way function so that the inverse calculation becomes easy, given a unique item of information only.

For example, if you compute the 4th power of 5, it's easy to calculate 5⁴ = 625. But if you are given with the number 625 and asked to find the two numbers a and b such that log_a 625 = b, it is going to take a lot longer to calculate. This sheer complexity in breaking security is the reason Public Key Cryptography is said to be the most significant development in cryptography in the past half a millennium year.

A prime example of it being extensively used in today's world is the RSA mechanism which was named after 3 MIT mathematicians Rivest, Shamir, and Adleman for key exchanging, digital signatures and encrypting different blocks of data. In fact, the RSA Data Security Inc. has designed a set of interoperable guidelines and standards for Public Key Cryptography, namely from Public Key Cryptography Standards, PKCS#1 to PKCS#15.

2) Secret Key Cryptography

Secret Key Cryptography technique uses a single key for both encryption and decryption. The message sender uses the key to encrypt the plaintext and sends the encrypted text or ciphertext to the receiver. The receiver applies the same key to decrypt the message and convert it to plaintext again.

Since a single key is used for performing both encryption and decryption operations, Secret Key cryptography is also called Symmetric Encryption.

An example where Secret Key Cryptography is used for a technological solution is in GPRS(General Packet Radio Service). Most GSM mobile phones use GPRS for data applications where GPRS uses a number of methods to offer different levels of data protection. Most common are GEA/1 and GEA/2 that uses a 64-bit key and a 96/128 bit key respectively. Most service providers today use either of these two GPRS protection techniques. Recently, GEA/3 and GEA/4 have also arrived though not widely deployed having a 128-bit key size for them and having advanced security features.

3) Hash Functions

Hash Functions also referred to as one-way encryption, are certain algorithms that use no definite key like the above two methods of cryptography. Instead, a hash value of fixed length is calculated based upon the plaintext, that makes the recovery of the plaintext and its length virtually impossible.

Hash Functions provide a method to preserve the integrity of a file by providing a digital fingerprint of the file's contents which is often used to determine whether a file has been altered by any external intruder/virus or not.

An example of Hash Functions being used for a technological solution is Secure Hash Algorithm(SHA) which are certain algorithms based on Secure Hash Standards(SHS). SHA includes several sub-algorithms like SHA-1, which produces a 160-bit hash value although it is deprecated now, SHA-2 which comprises 5 algorithms namely SHA-1 plus, SHA-224, SHA-256, SHA-384 and SHA-512 which produces hash values of 224, 256, 384 or 512-bits in length. Recently, SHA-3 was also started even though there haven't been any successful attacks on SHA-2 systems, to bolster existing SHA-2 systems to even further levels of impenetrable hash values for more advanced security.