IPSEC VPN CHAPTER 4 TERMINOLOGY Part 2

Diffie-Hellman(DH) Key Exchange

•Published in 1976 by Dr. Diffie & Dr.Hellman
•D-H is a public key cryptography program.
•It allows to peers to establish a Shared Secret Key Exchange used by Encryption algorithm (DES ,3DES ) over public network .

•It is defined in IKE Phase 1 configuration .

DH KEY CALCULATION

•It uses Prime Number (P)
•Prime Number can be divided by itself or 1 only without remainder.
•It also user Generator (G) , Secret Number a , b
•DH Algorithm calculates S1 for A and S2 B
•Then S1 AND S2 values exchanges between A & B.
•Using these values DH Algorithm calculates K1 for A and K2 for B.
•K1 AND K2 ARE SAME
•A and B will use this Sceret key.
•Note :- K1 AND K2 ARE NOT SHARED OVER PUBLIC NETWORK
• a and b secret values are also not shared over Public Network
• P and G are values are shared over Public Network

DH KEY CALCULATION EXAMPLE

Diffie-Hellman(DH) Groups.

DH Group determines the strength of the key exchange.

Hashing

•Data Integrity (no modifications / accuracy) is achieve by Hashing .
• Hashing Algorithm process on the data and results into a Hash Value or Checksum Value which is unique

 Step 1 – A will generate checksum value of data using Hashing algorithm.
•Step 2- A will send data along with data’s checksum value to B.
•Step 3 –B receives the data and runs the same Hashing algorithm to generate the Checksum value .
•Step 4 – B compares both the checksum values .
•If both values are same means B received unmodified data .

•Message – this is amartechstuff
•Hash value - 4046cff3102853721535b14ffc7458a9
•Its very difficult to generate message from Hash value.

Message Digest 5 (MD5)

•Designed by Ronald Rivest in 1991.
•Generates 128 bit Hash Value.
•MD5 has been exploited and MD5 hash value can be break .
•Can use in scenarios where there is almost no possibility of explosion
•Collision exists for numerous text / data.
•Can find number online tools for MD5 hashing

Secure Hash Algorithm (SHA) -Family

Thanks for Reading !!!!!

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