Cryptography and steganography

First of all start with the difference between these two. In simple words cryptography is a process of securing a message so that message is visible to everyone but no one can read it without authorized key and steganography is the process of hiding a message such that no one can see the message but once if message is found then anyone can read it without any key or password. So lets start with introduction of the above mentioned two terms.

Cryptography:

Basically cryptography is a technique to communicate securely between two person in presence of third party without their interference. More generally it is constructing protocols that overcome the influence of adversaries and which are related to various aspects such as data confidentiality, data integrity and authenticity. Application of cryptography includes ATM cards, password etc. key is needed to perform cryptography, this key is used as a password to encrypt and decrypt.

Cryptography is based on encryption and decryption of data. Encryption basically means converting simple text form into unintelligible form. Simple form of data is referred as plain textand encrypted data is called cipher/cypher text. Whereas converting cipher text into plain text is termed as decryption. An authorized rypt data. sender uses his key to encrypt data and reciever use the key to read the message.

-Modern cryptography:

Symmetric key cryptography-

It refers to the type of cryptography in which sender and receiver both uses same key. Symmetric key ciphers are implemented as either block cipher or stream cipher. A block cipher enciphers input in blocks of plaintext as opposed to individual characters, the input form used by a stream cipher. The Data Encryption Standard (DES) and the Advance Encryption standard (AES) are block cipher designs which have been designated cryptography standards by the US government (though DES's designation was finally withdrawn after the AES was adopted). Despite its deprecation as an official standard, DES (especially its still-approved and much more secure triple- DES variant) remains quite popular; it is used across a wide range of applications, from ATM encryption to e-mail privacy and secure remote access.

Stream ciphers, in contrast to the 'block' type, create an arbitrarily long stream of key material, which is combined with the plaintext bit-by-bit or character-by-character, somewhat like the one time pad. In a stream cipher, the output stream is created based on a hidden internal state which changes as the cipher operates.

Public Key cryptography-

Symmetric-key cryptosystems use the same key for encryption and decryption of a message, though a message or group of messages may have a different key than others. A significant disadvantage of symmetric ciphers is the key management necessary to use them securely. Each distinct pair of communicating parties must, ideally, share a different key, and perhaps each ciphertext exchanged as well. The number of keys required increases as the square of the number of network members, which very quickly requires complex key management schemes to keep them all straight and secret. The difficulty of securely establishing a secret key between two communicating parties, when a secure channel does not already exist between them.

Tools for cryptography:

1.TrueCrypt

2.PEncrypt

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