Question

Read all of the classic papers cited in Section 1.7. Compose a 500-1000 word paper (or 8 to 12 slide PowerPoint presentation) that summarizes the key concepts that emerge from these papers, emphasizing concepts that are common to most or all of the papers. cryptography

Answer 1

Cryptography is a key technology used for electronic data security. Cryptography (or cryptology) has its roots in Greek language. It has been derived from Greek word ‘kryptós’ which means ‘hidden,’ and the verb ‘gráfo’ means ‘write’ and ‘legein’ means ‘to speak’. Thus Cryptography means the study of message secrecy. The concise Oxford Dictionary (2006) defines cryptography as the art of writing or solving codes. Earlier, cryptography was treated as an art of disguising/scrambling the information so that the secret writing is not understandable to all except the actual recipient, who is aware of the technique of knowing the actual message passed. Anything in the world can be hidden from the sight and revealed again.

The basic idea of any cryptographic cipher is to disguise the confidential information in such a way that its meaning is not understandable to any unauthorized person. There can be two possible scenarios one may require disguising information is to save a file on a local machine or to save the information to be transferred over an insecure medium of communication, the Internet. The information to be concealed is called the plaintext (m) and the operation of disguising the information is called encryption. The encrypted plaintext is called the ciphertext or the cryptogram (c) and the set of rules used to encrypt the information is called the encryption algorithm (E). Normally the operation of this algorithm depends on some input used other than the message. This input is called encryption key (k). The receiver of the ciphertext or cryptogram has the decryption algorithm (D) which when used with the decryption key, produces the plaintext from the ciphertext or cryptogram. Any person who intercepts the message being communicated over the communication channel is called an interceptor.

Cryptography can be used to provide all the security services like:

1. Data integrity. The receiver may check that the communicated message was not modified during transmission. Using cryptography, one can add a message authentication code (MAC) on the message using his key and some code.

2. Authentication. The receiver should be able to verify the original sender.

3. Non-repudiation. The sender should not be able to deny that he has not sent the message. Whitfield Diffie and Martin Hellman produced the electronic equivalent to the hand-written signatures in the paper New Directions in Cryptography, used as digital signatures that the sender attaches with the message.

4. Confidentiality. Transmitted message should not be visible to all. It should only be viewed by its intended receiver. Using encryption algorithms, one can transform the original message into some non-readable form that is only understandable by the receiver after applying decryption algorithm.

Use of Cryptographic algorithms

Cryptographic encryption algorithms may be used statically and dynamically. Encryption of data before sending it to the storage servers is generally carried out by special cryptographic Network Interface Cards (NICs) called static encryption. It is a fast process done offline by the desktop or intermediate server also known as store and forward servers that are in the networks. In this case, the encryption key is stored with the encrypted data while it is on the intermediate machine doing encryption. If someone gains unauthorized access to that intermediate server, entire data can be decrypted.

Effectiveness of Cryptographic algorithms

Cryptographic algorithms use key and algorithm that is used to convert the message to ciphertext using a key. The ciphertext is then converted back to the original message using decryption algorithm and a key at the receivers’ end. Hence, encryption-decryption is the procedure that is used to apply the science of cryptography to ensure the confidentiality of messages being communicated. Generally, the algorithm is large, usually a combination of mechanical or electronic device(s), or based on some complex mathematical procedure. But the algorithm cannot be kept secret. Thus the overall security of any cryptographic system is dependent on the secrecy of the key. Moreover, one cannot be sure about the breaking of any of the cryptosystems even after providing some mathematical proof that the system cannot be cracked. A cryptographic system may be secure for one purpose but not for other depending on the demand of keeping the information secure for certain period of time. A cryptosystem that cannot be broken at present may succumb to cryptanalysts in the near future.