Diffie Helman, Symmetric and Asymmetric Encryption
Symmetric Encryption has two potential drawbacks. The first of these is the commonly known Man in the Middle attack. The second is a limitation on reuse.
Man in the Middle attack – Symmetric
If Anuj wants to communicate with Bob, Tom can intercept the channel (both ways) – and replace Anuj’s random number with his own. He can also replace Bob’s random number with his own. And neither will know that their numbers have been replaced.
Re-Use Limitation – Symmetric Keys
If Anuj wants to communicate with Bob and Charlie, Anuj needs TWO separate keys (cannot re-use the same key).
No Re-Use Limitation – Asymmetric Keys
Asymmetric keys can be used by as many of Anuj’s contacts as needed. The same key pair works. Everyone uses the SAME PUBLIC key to encrypt their data.
Basic Diffie Helman
Anuj and Bob agree on TWO prime numbers (both large). Call them g and n . These do not have to be secret (private). They can be publicly known.
Anuj chooses a random number x. Computes A = ( g ^ x ) mod n
Bob chooses a random number y. Computes B = ( g ^ y ) mod n
They exchange A and B (using either offline or online exchange). Using A and B, they both compute a secret key. This key ends up being the SAME for both of them, even though they both started with different random numbers.
Now, they can happily encrypt all future messages using their secret key
Anuj holds professional certifications in Google Cloud, AWS as well as certifications in Docker and App Performance Tools such as New Relic. He specializes in Cloud Security, Data Encryption and Container Technologies.
Anuj Varma – who has written 1210 posts on Anuj Varma, Hands-On Technology Architect, Clean Air Activist.
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