Homework SourseAnswer questions 1115 with a short paragraph of 59 lines 11P
Answer questions 11-15 with a short paragraph of 5-9 lines.
11.Public Key Cryptography:
Examples are:
12.Steganography is
Example of steganography is:
13.Symmetric Key Algorithms:
Examples are:
14.Discuss the following concepts: RSA (Rivest, Shamir, Adleman):
15.What are PGP key sizes:
Solution
Answers:
11.Public Key Cryptography:
-> Public Key Cryptography was discovered by R. Rivest, A. Shamir and L.Adleman .
->This method has been widely used to ensure security and secrecy in electronic communication and particularly where financial transactions are involved.
->The private key pair is used to decrypt messages, and this key will only work if the public key of the same site was used to encrypt the message. That is to say, Site B\'s public key is obtained from a directory, then used by Site A to encrypt a message for them.
-> The Public Key Cryptography is to send messages in such a way that only the person who receives them can understand them even if the method of encryption is discovered by \'an enemy\' who intercepts the messages.
-> The method depends on the fact that while it is easy to calculate the product of two large prime numbers.
example:
->Let two primes be a= 7 and b= 13. Thus, modulus n = ab = 7 x 13 = 91.
12)Steganography is
->Steganography is the hiding of a secret message within an ordinary message and the extraction of it at its destination.
->Steganography takes cryptography a step farther by hiding an encrypted message so that no one suspects it exists.
-> The difference between steganography and cryptography is that in cryptography, one can tell that a message has been encrypted, but he cannot decode the message without knowing the proper key.
-> In steganography, the message itself may not be difficult to decode, but most people would not detect the presence of the message.
example:
For example, one could hide a text message within a paragraph of words, so that by isolating every 10th word, the secret message can be detected.
13)Symmetric Key Algorithms:
-> symmetric key algorithms are used primarily for the bulk encryption of data or data streams.
->These algorithms are designed to be very fast and have a large number of possible keys.
-> it is used for the same cryptographic keys for both encryption ofplaintext and decryption of ciphertext.
->The keys may be identical or there may be a simple transformation to go between the two keys.
Types of symmetric-key algorithms:
a)Stream ciphers encrypt the digits (typically bytes) of a message one at a time.
b)Block ciphers take a number of bits and encrypt them as a single unit, padding the plaintext so that it is a multiple of the block size. Blocks of 64 bits were commonly used.
-> Symmetric cryptography was well suited for organizations such as governments, military, and big financial corporations were involved in the classified communication.
14) RSA:
->This cryptosystem is one the initial system. It remains most employed cryptosystem even today. The system was invented by three scholars Ron Rivest, Adi Shamir, and Len Adleman and hence, it is termed as RSA cryptosystem.
-> Public Key Cryptography was discovered by R. Rivest, A. Shamir and L.Adleman .
->Two aspects of the RSA cryptosystem, firstly generation of key pair and secondly encryption-decryption algorithms.
a)Find Derived Number
b)Generate the RSA modulus (n)
15) What are PGP key sizes:
PGP gives you choices for RSA and DSA key size ranging from 512 to 2048 or even 4096 bits. The larger the key, the more secure the RSA/DSA portion of the encryption is a 1024 bit key can take 8 times longer to generate than a 384 bit key.
