CRYPTOGRAPHY

OVERVIEW:-

Cryptography is the study of secure communications techniques that allow only the sender and intended recipient of a message to view its contents. The term is derived from the Greek word kryptos, which means hidden. It is closely associated to encryption, which is the act of scrambling ordinary text into what's known as ciphertext and then back again upon arrival. In addition, cryptography also covers the complicate of information in images using techniques such as microdots or merging. Ancient Egyptians were known to use these methods in complex hieroglyphics, and Roman Emperor Julius Caesar is credited with using one of the first modern ciphers.

INTRODUCTION

CryptoGraphy is a technique of securing information and communications via use of secret  codes so that only the relevant identity can understand it and process it. Thus preventing un-authorized access to information. The prefix "crypt" means "hidden" and suffix "graphy" means "writing". In cryptography, the techniques  which are used to protect information are obtained from the concepts of mathematics and calculations which are based on set of rules known as algorithms in such a way that it becomes hard to decode it. These algorithms are also useful in digital signing, verification to protect data privacy, cryptographic key generation, web browsing on internet and to safeguard confidential transactions such as your bank transactions. 

Processes involved in CryptoGraphy:-

Cryptography is associated with the process where the normal text is converted into cipher text or in hidden form which is text made such only the intended receiver can decode it and this process is known as encryption, and the process of conversion of cipher text to normal text is known as decryption.

Features Of CryptoGraphy:-

1. Confidentiality - Information can only be accessed by the person for whom it is intended and no other person except him can access it.
2. Non-Repudiation - The sender of information cannot deny his or her intention to send information at later stage.
3. Authentication - The identities of sender and receiver are confirmed. As well as the information about the origin and destination of information is confirmed.
4. Integrity - Information cannot be modified in storage or in transition between sender and receiver  without any addition to information being detected.

Types of CryptoGraphy:-

1.Symmetric Key Cryptography - Symmetric key cryptography is any cryptographic algorithm that is based on a shared key that is used to encrypt or decrypt text/cyphertext, in contract to asymmetric key cryptography, where the encryption and decryption keys are different. 

Symmetric encryption is generally more efficient than asymmetric encryption and therefore preferred when large amounts of data need to be exchanged.

Establishing the shared key is difficult using only symmetric encryption algorithms, so in many cases, an asymmetric encryption is used to establish the shared key between two parties. Examples for symmetric encryption key cryptography include ADVANCED ENCRYPTION STANDARD, DATA ENCRYPTION STANDARD, and 3DES. Key exchange protocols used to establish a shared encryption key include DIFFIE-HELLMAN(DH), elliptic curve and RSA. 

2.Hash Functions - A cryptographic hash function is an algorithm that takes an arbitrary amount of data input—a credential—and produces a fixed-size output of encode text called a hash value. That encoded text can then be stored instead of the password itself, and later used to verify the user.

Certain properties of cryptographic hash functions impact the security of password storage.

• Non-reversibility. A good hash should make it very hard to reconstruct the original password from the output or hash.
• Diffusion. A change in just one bit of the original password should result in change to half the bits of its hash. In other words, when a password is changed slightly, the output of enciphered text should change significantly and unpredictably.
• Determinism. A given password must always generate the same hash value or enciphered text.
• Collision resistance. It should be hard to find two different passwords that hash to the same enciphered text.
• Non-predictable. The hash value should not be predictable from the password.

3.Asymmetric Key Cryptography - Asymmetric keys are the foundation of Public Key Infrastructure (PKI) a cryptographic scheme requiring two different keys, one to lock or encrypt the plaintext, and one to unlock or decrypt the cyphertext. Neither key will do both functions. One key is published (public key) and the other is kept private (private key). If the lock/encryption key is the one published, the system enables private communication from the public to the unlocking key's owner. If the unlock/decryption key is the one published, then the system serves as a signature verifier of documents locked by the owner of the private key. This system also is called asymmetric key cryptography.

  "Cryptography is the essential building block of independence for organisations on the Internet, just like armies are the building block of Countries, because otherwise one country just takes over another"

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