How are IVs used in association with RSA Encryption?

Can someone explain why we use them in this RSA context?

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    $\begingroup$ We do not speak of IVs in context of public key encryption such as RSA encryption. I think what you mean is random padding. This is used in order to make the RSA encryption probabilistic (encrypting same message twice under the same key yields different ciphertexts with overwhelming probability). This is required to make public key encryption secure in stronger security models (such as IND-CPA and IND-CCA) and rules out trivial "trial and error - test-encrypt messages" attacks. $\endgroup$ – DrLecter Oct 31 '13 at 9:58
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    $\begingroup$ What's funny about using random padding is that we usually encrypt random symmetric keys (as part of hybrid encryption), a scenario where randomness isn't actually required. $\endgroup$ – CodesInChaos Oct 31 '13 at 11:22

IV is not commonly used in RSA Encryption.

Do you mean:

  1. AES Encryption? AES Encryption in some modes, for instance CBC or CFB uses IV (Initial Vector), which is (often) unpredictable value that never repeats for the same key. It is fairly common to generate IV randomly
  2. Random padding in RSA Encryption? There are several padding mechanisms defined for RSA Encryption, including e.g. PKCS#1v1.5 padding and OAEP. In RSA encryption, parts of the padding commonly are random, just like some IV's used for symmetric encryption.

In case you are thinking of RSA Encryption padding where IV is actually used, please, provide name of the padding scheme in the question.


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