Date post: | 08-Aug-2015 |
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Cryptography
Presented By:Sanjeev Kumar
Dept: I.T
Cryptography Intro
Why Encrypt?• Protect stored information
• Protect from Unauthorized disclosure
Encryption - process by which plaintext is converted to cipher text using a key
Decryption - process by which cipher text is converted to plaintext (with the appropriate key)
plaintext (clear text)- intelligible data
Cryptography Terminology
Cryptography - art/science relating to encrypting, decrypting information
Cryptanalysis - art/science relating to converting cipher text to plaintext without the (secret) key
Here we have three types of algorithms that we can talk about:
MODERN CRYPTOGHRAPHY
Secret Key Cryptography
Hash Functions
Public Key Cryptography
MODERN CRYPTOGHRAPHY
Secret key
Here we have three types of algorithms that we can talk about:
MODERN CRYPTOGHRAPHY
Secret Key Cryptography
Hash Functions
Public Key Cryptography
MODERN CRYPTOGHRAPHY
Secret key
Secret Key(Symmetric) Cryptography uses a single key for both encryption and decryption.
SECRET KEY CRYPTOGHRAPHY
A single key is used
SECRET KEY CRYPTOGHRAPHY
Sender uses the key to encrypt
Receiver uses the same key to decrypt
Key must be known to both the sender and the receiver
The difficulty is the distribution of the key
Secret key cryptography algorithms that are in use today :
SECRET KEY CRYPTOGHRAPHY
Data Encryption Standard (DES):
Advanced Encryption Standard (AES):
International Data Encryption Algorithm (IDEA):
SECRET KEY SUMMARY
Hash functions(One-way cryptography) have no key since plaintext cannot be recovered from the ciphertext.
HASH FUNCTIONS
Called message compiler and one-way encryption
HASH FUNCTIONS
No key is used
Digital fingerprint
Provide the integrity
Hash algorithms that are in common use today:
HASH FUNCTIONS
Message Digest (MD) algorithms:
HAVAL (Hash of Variable Length):
Tiger:
PUBLIC KEY CRYPTOGHRAPHY
Public Key(Asymmetric) Cryptography. Two keys are used. One for encryption, one for decryption.
PUBLIC KEY CRYPTOGHRAPHY
Developed in the last 300-400 years.
Martin Hellman and graduate student Whitfield Diffie
A two-key crypto system
Mathematical functions
Public key Cryptography
Secret key Cryptography
Secret Key Cryptography
With secret key cryptography, a single key is used for both encryption and decryption. As shown in Figure 1A, the sender uses the key (or some set of rules) to encrypt the plaintext and sends the ciphertext to the receiver. The receiver applies the same key (or ruleset) to decrypt the message and recover the plaintext. Because a single key is used for both functions, secret key cryptography is also called symmetric encryption.
Secret Key Cryptography
Public-Key Cryptography
Generic PKC employs two keys that are mathematically related although knowledge of one key does not allow someone to easily determine the other key. One key is used to encrypt the plaintext and the other key is used to decrypt the ciphertext. The important point here is that it does not matter which key is applied first, but that both keys are required for the process to work (Figure 1B). Because a pair of keys are required, this approach is also called asymmetric cryptography.
Public-Key Cryptography
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