Cryptology ePrint Archive: Report 2010/135

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

Aur\'elie Bauer and Jean-S\'ebastien Coron and David Naccache and Mehdi Tibouchi and Damien Vergnaud

Abstract: 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.

Category / Keywords: public-key cryptography / PKCS \#1 v1.5, Encryption, Broadcast Encryption, Cryptanalysis

Publication Info: To appear in the proceedings of ACNS 2010 (full version)

Date: received 12 Mar 2010, last revised 14 Apr 2010

Contact author: aurelie bauer at ens fr

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Version: 20100414:084627 (All versions of this report)

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