During my master thesis I came across RSA-PSS-R which is in my opinion a quite elegant way of saving bandwidth and space using digital signature. But I didn't find any information about any real world implementation out there. I have the feeling that it's exactly like the Schnorr Signature scheme. Everybody says that it is very efficient, but no one actually uses it.

Maybe I didn't dig deep enough but is there anyone out there actually using message recovery AT ALL in any real world implementation?

Thank you for your feedback

  • $\begingroup$ My guess is that since in real world one uses the "hash then sign" paradigm (i.e., hash a message and sign the hash value) a signature scheme with message recovery does not really give an added value, since you can only recover the hash value (which, due to the one-wayness of the hash function will not let you recover the message itself). $\endgroup$ – DrLecter Nov 14 '13 at 15:29
  • $\begingroup$ @DrLecter Even when using a hash as part of the signature one could put the (beginning of the) message into the remaining space. $\endgroup$ – CodesInChaos Nov 14 '13 at 17:18
  • $\begingroup$ @CodesInChaos yes thats true. Actually I did not think of very small message spaces :/ Clearly, in authentication protocols and resource constraint environments that feature could actually make sense. Didn't think of that either :) $\endgroup$ – DrLecter Nov 14 '13 at 17:29

A signature scheme with message recovery is standardized as ISO/IEC 9796-2 (link to preview). Scheme 1 in this standard is commonly used in the Smart Card industry, despite its known weaknesses in a chosen-message setup.

Example real-life uses include the EMV banking application (the free documents linked there include a description of an industry-standard subset of ISO/IEC 9796-2 Scheme 1; there is support for this subset in JavaCard 2.2.2 and up); and the certificates in the European Digital Tachograph system (head to Annex 1B, appendix 11).

Update: As kindly pointed by Maarten Bodewes, that is also used in ICAO e-passport specifications, appendix 4.

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  • $\begingroup$ Not to mention ICAO specifications for passports which use it in the Active Authentication protocol - although for that it is only used within a challenge response protocol (the challenge is recovered). Tacho also uses it for certificates, if I'm not mistaken. $\endgroup$ – Maarten Bodewes Nov 14 '13 at 16:49
  • $\begingroup$ I will have a look at it. Thx for the advice $\endgroup$ – Mr Anderson Nov 15 '13 at 14:53

Some implementations of RSA PKCS#1v1.5 use message recovery to find out which hash function was applied.

PKCS#11 API defines the C_SignRecover and C_VerifyRecover and allow them to be used with the most RSA mechanisms. Long story short: this means that there is very widely available API which allows the functionality. Thus, it is likely that quite a few pieces of software use it in practice.

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