Identity-based cryptography: Difference between revisions

Revision as of 15:50, 29 July 2021

Revision as of 01:43, 30 July 2021

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|last = Cocks

|first = Cliff

|title = Cryptography and Coding
|chapter = An Identity Based Encryption Scheme Based on Quadratic Residues

|journal = Lecture Notes in Computer Science

|year = 2001

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|series = Institute of Mathematics and Its Applications International Conference on Cryptography and Coding – Proceedings of IMA 2001

|pages = 360–363

|chapter-url = http://www.cesg.gov.uk/site/ast/idpkc/media/ciren.pdf

|publisher = Springer

|doi = 10.1007/3-540-45325-3_32

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}}</ref><ref>{{cite web|archive-url=https://web.archive.org/web/20150627063023/http://www.bristol.ac.uk/pace/graduation/honorary-degrees/hondeg08/cocks.html|archive-date=2015-06-27|url=http://www.bristol.ac.uk/pace/graduation/honorary-degrees/hondeg08/cocks.html|publisher=University of Bristol|title=Dr Clifford Cocks CB, Honorary Doctor of Science}}</ref>

Closely related to various identity-based encryption schemes are identity based key agreement schemes. One of the first identity based key agreement algorithms was published in 1986, just two years after Shamir's identity based signature. The author was E. Okamoto.<ref>{{Cite journal|last=Okamoto|first=E.|date=1986|title=Proposal for identity-based key distribution systems|journal=Electronics Letters|volume=22|issue=24|pages=1283–1284|doi=10.1049/el:19860880|bibcode=1986ElL....22.1283O|issn=0013-5194}}</ref> Identity Based key agreement schemes also allow for "escrow free" identity based cryptography. A notable example of such an escrow free identity based key agreement is the McCullagh-Barreto's "Authenticated Key Agreement without Escrow" found in section 4 of their 2004 paper, "A New Two-Party Identity-Based Authenticated Key Agreement."<ref>{{Cite journal|lastlast1=McCullagh|firstfirst1=Noel|last2=Barreto|first2=Paulo S. L. M.|date=2004|title=A New Two-Party Identity-Based Authenticated Key Agreement|url=https://eprint.iacr.org/2004/122}}</ref> A variant of this escrow free key exchange is standardized as the identity based key agreement in the Chinese identity based standard [[SM9 (cryptography standard)|SM9]].

==Usage==

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==Limitation==

Identity-based systems have a characteristic problem in operation. Suppose Alice and Bob are users of such a system. Since the information needed to find Alice's public key is completely determined by Alice's ID and the master public key, it is not possible to revoke Alice's credentials and issue new credentials without either (a) changing Alice's ID (usually a phone number or an email address which will appear in a corporate directory); or (b) changing the master public key and re-issuing private keys to all users, including Bob.<ref name=green1>{{Cite journal |title=Forward Secure Asynchronous Messaging from Puncturable Encryption |archive-url=https://archive.is/tQs8D |doi=10.1109/SP.2015.26 |archive-date=8 June 2021 |publication-date=20 July 2015 |date=17 May 2015 |url=https://ieeexplore.ieee.org/document/7163033 |publisher=ACM |last1=Green |first1=Matthew |last2=Miers |first2=Ian |journal=SP '15: Proceedings of the 2015 IEEE Symposium on Security and Privacy |pages=305–320 |isbn=978-1-4673-6949-7 |s2cid=9171925 }}</ref>

This limitation may be overcome by including a time component (e.g. the current month) in the identity.{{r|green1}}