Encryption Technique

Encryption Techniques

Keerthana.J

(060341039)

Topics Covered

Types of Attacks Cryptography Traditional methods Symmetric and Public-Key Algorithms Digital Signatures Certificates Cryptography with PHP

Types of Threat in Internet

Threat is a set of circumstances that has the potential of causing loss and harm

Interception Interruption Modification Fabrication

Cryptography

Encryption is the process of translating information from its original form (called plaintext) into an encoded, incomprehensible form (called ciphertext).

Decryption refers to the process of taking ciphertext and translating it back into plaintext.

What does it provide ?

Important aspects of computer security Confidentiality Integrity Availability Authenticity of data

Traditional Methods

1) Substitution Ciphers

a b c d e fghi j k l mno pqr s t u vwx y z

KEY: QWERTYUIOPASDFGHJKLZXCVBNM

Plaintext : attack

Ciphertext : QZZQEA

2)Transposition Cipher

M E G A B U C K (KEY)

7 4 5 1 2 8 3 6

t r a n s f e r

o n e m i l l I

o n t o a c c o

u n t s i x t w

w o t w o Plaintext : transferonemilliontoaccountsixtwotwo Ciphertext : nmoswsiaioelctrnnnoaetttrlowtoouwflcx

Symmetric-Key Algorithms

Traditional Vs Symmetric-Key It uses the same key for encryption and

decryption The key is called the secret key. Drawback of Symmetric-key algorithms Examples : Data Encryption Standard

Advanced Encryption Standard

Public-Key Algorithms

New kind of cryptosystem where the encryption and the decryption keys are different.

Public Keys used by the entire world for encrypting messages to send it to the user.

Private Keys which the user needs for decrypting messages.

Examples : RSA, Knapsack algorithm

Working of Public-Key Algorithms

Drawbacks in Public-Key Algorithm

There were some drawbacks in Public-Key Algorithms which led to Digital Signatures.

The receiver could not verify the identity of the sender.

The sender cannot later repudiate the contents of the message.

The receiver could possibly have concocted the message himself.

Digital Signatures

Symmetric-Key SignaturesIt has a central authority that knows everything and whom everyone trusts.Drawback is everyone has to believe in the third party and he gets to read all the signed messages.

Public-Key Signatures These drawbacks are solved in this kind of signatures. Any public-key algorithm can be used for digital signatures.

Working of Public-Key Signatures

Certificates

Public key cryptography makes it possible for people who do not share a common key to communicate securely.

It also makes signing messages possible without the presence of a trusted third party.

An organization that certifies public keys is now called a (Certification Authority) CA.

Used in Credit card payments

Example of Certificate

The fundamental job of a certificate is to bind a public key to the name of a principal (individual, company)

Encryption in PHP

One Way EncryptionThe algorithms for one-way encryption are called hash algorithms. PHP uses the Message Digest (MD) hash algorithm, MD5, for one-way encryption.Examples: Used for storing user passwords.

<?php $msg = " Password "; $encrypted_text = md5 ($msg); echo("<b>Plain Text : </b>"); echo($msg); echo("<p><b>Encrypted Text : </b><br>"); echo($encrypted_text); ?>

Output

PlainText : Password

Encrypted Text : 3f13fa96ed14d842519897db6810aa7

Symmetric Encryption

PHP provides several algorithms for symmetric encryption in the mcrypt library. It also provides the mcrypt_ecb function to implement the algorithms of the mcrypt library.

Asymmetric Encryption

Complex to implement but very efficient.

<?php echo("<h3> Symmetric Encryption </h3>"); $key_value = "KEYVALUE";

$plain_text = "PLAINTEXT"; $encrypted_text = mcrypt_ecb(MCRYPT_DES, $key_value,

$plain_text, MCRYPT_ENCRYPT); echo ("<p><b> Text after encryption : </b>"); echo ( $encrypted_text ); $decrypted_text = mcrypt_ecb(MCRYPT_DES, $key_value,

$encrypted_text, MCRYPT_DECRYPT); echo ("<p><b> Text after decryption : </b>"); echo ( $decrypted_text ); ?>

Conclusion

The various algorithms are selected as per the security levels required for the data.

It is the responsibility of the developer to include proper encryption of the data.

These basic cryptographic algorithms are used to implement SSL (Secure Socket Layer) for web security.

Thank You