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Ciphertext Indistinguishability

Ciphertext indistinguishability (IND-CPA/CCA) requires that an attacker cannot distinguish the encryptions of two equal-length plaintexts; it is the standard definition of encryption security.

Purpose

It provides the provable-security goal for symmetric and public-key encryption, with IND-CCA2 being the strongest standard.

Mechanism

Security game: the adversary picks m0 and m1, the challenger returns E(mb), and the adversary guesses b. IND-CPA allows an encryption oracle; IND-CCA1 allows a decryption oracle (before the challenge); IND-CCA2 allows a decryption oracle (the challenge ciphertext excepted).

Use cases

  • Encryption security proofs
  • Cryptographic protocol design
  • Security-level assessment

Related tools

AES Encryptor
Encrypt text or binary data with AES (CBC/GCM/ECB) using Web Crypto API. Free, private, and 100% client-side.
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RSA Tool
RSA key generation, encryption, decryption, signing, and verification using Web Crypto API. Free, private, and 100% client-side.
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References