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Lecture 9: Encryption Schemes (II)

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Recap: EAV-security of encryption schemes

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Recap: One-time pad (perfectly EAV-secure)

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  • Lesson: EAV-security is one-time in nature
    • Reuse key to encrypt multiple messages, 1 message leaked → all messages leaked
  • Key should not be reused

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  • If you want to reuse key → need stronger security definition (and new scheme)

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Chosen-Plaintext Attacks

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CPA-security

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CPA-security

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CPA-security

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CPA-Secure Encryption Scheme

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