Paper 2010/135

On The Broadcast and Validity-Checking Security of PKCS \#1 v1.5 Encryption

Aurélie Bauer, Jean-Sébastien Coron, David Naccache, Mehdi Tibouchi, and Damien Vergnaud


This paper describes new attacks on PKCS \#1 v1.5, a deprecated but still widely used RSA encryption standard. The first cryptanalysis is a broadcast attack, allowing the opponent to reveal an identical plaintext sent to different recipients. This is nontrivial because different randomizers are used for different encryptions (in other words, plaintexts coincide only partially). The second attack predicts, using a single query to a validity checking oracle, which of two chosen plaintexts corresponds to a challenge ciphertext. The attack's success odds are very high. The two new attacks rely on different mathematical tools and underline the need to accelerate the phase out of PKCS \#1 v1.5.

Available format(s)
Public-key cryptography
Publication info
Published elsewhere. To appear in the proceedings of ACNS 2010 (full version)
PKCS \#1 v1.5EncryptionBroadcast EncryptionCryptanalysis
Contact author(s)
aurelie bauer @ ens fr
2010-04-14: revised
2010-03-12: received
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Creative Commons Attribution


      author = {Aurélie Bauer and Jean-Sébastien Coron and David Naccache and Mehdi Tibouchi and Damien Vergnaud},
      title = {On The Broadcast and Validity-Checking Security of PKCS \#1 v1.5 Encryption},
      howpublished = {Cryptology ePrint Archive, Paper 2010/135},
      year = {2010},
      note = {\url{}},
      url = {}
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