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while reading Introduction to modern cryptography by Katz and Lindell, I came across these two experiments:

eav enter image description here

For me, they look like it's the same thing. Can you please explain me the difference? Thanks :)

Souphiane Bensalim
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  • Welcome to Cryptography. Did you read the context before the algorithms? I feel like you're dumping just these two for us. The first one is for the multiple messages and the adversary type. Can you see that the first adversary has oracle access as the second one? – kelalaka Oct 01 '22 at 17:41
  • You should check what eavesdropping adversary and a CPA- Adversary. – kelalaka Oct 01 '22 at 17:42
  • Hi, thanks for the reply. Yes, I've read the context and I know that CPA in contrast to EAV is an adversary that can exercise control over what the honest parties encrypt, while EAV only sees the ciphertexts without control over what gets encrypted. I just see the two games somehow equivalent and I don't get why from the game description the adversary in the first game (multiple eav) is weaker than in the second (cpa). – Souphiane Bensalim Oct 01 '22 at 17:50
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    Because each time we give more power to the adversary. And each notion has real-life examples. And, even we don't stop there and give more power to the adversaries. – kelalaka Oct 01 '22 at 18:04

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