CRYPTOGRAPHY SANDHIYA S RANJTHA B
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CRYPTOGRAPHY
SANDHIYA SRANJTHA B
CRYPTOGRAPHIC TERMINOLOGY
• PLAIN TEXT: The format of the data before encrypted.
• CIPHER TEXT: The scrambled format of data after being encrypted.
• ENCRYPTION: Method of transforming plain text into an unreadable format.
• DECRYPTION: Method of obtaining the encrypted text into plain text.
What is Cryptography
The art of protecting information by transforming it (Encrypting it) into an unreadable format, called Cipher text, only those who posses a secret key can Decipher or (Decrypt) the message into Plain text.
WHY WE NEED A CRYPTOGRAGHY
• For confidentiality
• For authentication
• For data integrity
BASIC CONCEPT OF CRYPTOGRAPHY
SYMMETRIC KEY ENCRYPTION
TYPES OF SYMMETRIC
ENCRYPTION oSUBSTITUTION CIPHERoTRANSPOSTION CIPERoVERNAM CIPER
A- 0B- 1C- 2D- 3E- 4F- 5G- 6H- 7I- 8J- 9K- 10L- 11M-12N- 13O- 14P- 15Q- 16R- 17S- 18T- 19U- 20V- 21W-22X- 23Y- 24Z- 25
PUBLIC /PRIVATE KEY
• A public key known to everyone • private or secret key known only to the
recipient of the message• When John wants to send a secure
message to Jane, he uses Jane's public key to encrypt the message. Jane then uses her private key to decrypt it.
ASYMMETRIC KEY ENCRYPTION
TYPES OF ASYMMETRIC ALGORITHMS
DIFFIE-HELLMANRSAEI GAMALELLIPTIC CURVE CRYPTOGRAPHY(ECC)
DIFFIE-HELLMAN METHOD
Alice and Bob were communicating each other via mail
Eve trying to hack the message To avoid hacking they are using
DIFFIE-HELLMAN METHOD
EXAMPLE FOR DIFFIE-HELLMAN METHOD
alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
Alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN METHOD
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Eve
Alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN METHOD
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
EXAPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15Random Number=13
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15Random Number=13
315 mod 17=6313mod 17=12
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15Random Number=13
315 mod 17=6 12 = 313mod 17
6
6
12
12
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15Random Number=13
315 mod 17=6 12 = 313mod 17
6
6
12
12
1215mod 17=10 613mod17=10
EXAMPLE FOR DIFFIE-HELLMAN METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15Random Number=13
315 mod 17=6 12 = 313mod 17
6
6
12
12
1215mod 17=10 613mod17=10
36mod17=15312mod17=4
EXAMPLE FOR DIFFIE-HELLMAN METHOD
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