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what is cryptograrhy?????????????????????????????????

what is cryptograrhy?????????????????????????????????
 

Grade:12

2 Answers

Umakant biswal
5349 Points
7 years ago
@ sivagiri 
Cryptography refers to the method of storing and transmitting data in a perticular form , so, that only those for whoom it is intended can read and process it . 
u can simply tell , its a type of writting or solving the codes . 
BELOW ARE THE SOME CRYPTOGRAPHIC ALGORITHM I AM GIVING , KINDLY REFER TO TAHT IF U CAN UNDERSTAND . 
DES. This is the 'Data Encryption Standard'.
RSA. RSA is a public-key system designed by Rivest, Shamir, and Adleman
HASH. A 'hash algorithm' is used for computing a condensed representation of a fixed length message/file
THE other ones are 
MD5 , 
AES 
HMAC , SHA – 1
hope it clears your doubt 
ALL THE BEST ..
 
jyoti bhatia
202 Points
7 years ago
Cryptography is the science of providing security for information. It has been used as a means of providing secure communication between individuals, government agencies and military forces. Today, cryptography is a cornerstone of modern security technologies used to protect information and resources on both open & closed networks.
If one wants to keep information secret, one has two possible strategies hide existence of information or make information unintelligible. Cryptography is the art and science of keeping information secure from unintended audiences, of encrypting it. Conversely, cryptanalysis is art & science of breaking encoded data. Branch of mathematics encompassing both cryptography and cryptanalysis is cryptology.
Modern Cryptography uses sophisticated equations (algorithms) and secret keys to encrypt and decrypt data.
 
Today, cryptography is used to provide secrecy and integrity to one’s data and both authentication and anonymity to one’s communication.
Cryptology was public field in United States until World War I, when Army & Navy realized its value to national security and began working in secret. Through early 1970s, cryptology was dominated by government both because computers were very expensive and because government released very little information. It returned to mainstream academic and scientific communities in a sort of cryptology renaissance when computer revolution made computers more readily available when demand for encryption increased due to fundamental changes in the ways America communicated.
Increase in demand for cryptography was driven by industry interest (e.g., financial services required secure electronic transactions & businesses needed to secure trade secrets stored on computers) and individual interest (e.g., secure wireless communications). Digital communications were obvious candidates for encryption.
Principles of Modern Cryptography:
Modern cryptographers emphasize that security should not depend on secrecy of encryption method, only secrecy of the keys. Secret keys must not be revealed when plaintext and ciphertext are compared and no person must have knowledge of the key. Modern algorithms are based on mathematically difficult problems – for example, prime number factorization, discrete logarithms, etc. there is no mathematical proof that these problems are in fact hard, just empirical evidence.
Modern cryptographic algorithms are too complex to be executed by humans. Today’s algorithms are executed by computers or specialized hardware devices and are implemented in computer software.
Design of secure systems using encryption techniques focuses mainly on protection of secret keys. Keys can be protected either by encrypting them under other keys or by protecting them physically, while algorithm used to encrypt data is made public and subjected to intense security. When cryptographers hit on an effective method of encryption (a cipher), they can patent it as intellectual property and earn royalties when their method is used in commercial products. In current open environment, many good cryptographic algorithms are available in major bookstores, libraries and on Internet or patent office.
Symmetric and Asymmetric Algorithms:
There are two types of key-based encryption, symmetric (secret-key) and asymmetric (public key) algorithms. Symmetric algorithms use same key for encryption and decryption, while asymmetric algorithms use a different key for encryption and decryption and decryption key cannot be derived from encryption key.
Symmetric algorithms can be divided into stream ciphers and block ciphers. Stream ciphers can encrypt a single bit of plaintext at a time whereas block ciphers take a number of bits and encrypt them as a single unit. An example of a symmetric algorithm is DES.
 
Asymmetric ciphers (also called public-key cryptography0 make a public key universally available, while only one individual possesses private key. When data is encrypted with public key, it can only be decrypted with private key and vice versa. Public key cryptography adds a significant benefit – it can serve to authenticate a source (e.g. a digital signature). An example of an asymmetric algorithm is RSA.
 
In general, symmetric algorithms execute much faster than asymmetric ones. In real applications, they are often used together while random key encrypts actual message using a symmetric algorithm. This combination is referred to as a digital envelope.

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