Diffie-Hellman key exchange


Diffie-Hellman – Layman terms

Basic info (table 1):

(2x)y = 2xy = (2y)x

For DH, x and y are very large numbers.

Step 1: GB selects a large random number, x.

Step 2: GB raises 2 to the power of x and obtains, say G (=2x).

Step 3: GB sends G to SB.

Step 4: SB selects a large random number, y.

Step 5: SB raises 2 to the power of y and obtains, say S (=2y).

Step 6: SB sends S to GB.

Step 7: Following calculations are performed

SB calculations GB calculations
Sx Gx
(2y)x from Step 5 (2x)y from Step 2
2yx from table 1 2xy from table 1
(2x)y from table 1 (2x)y from table 1

Step 8: Both SB and GB now has a shared secret without actually have to transfer the key.

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