[Cryptography] What is "chameleon hash"?

Dmitry Belyavsky beldmit at gmail.com
Fri Jul 7 15:44:54 EDT 2017


Hello,

There is a very useful bitcoin-related article "The Blockchain Immutability
Myth" by Gedeon Greenspan

http://www.multichain.com/blog/2017/05/blockchain-immutability-myth/


"With this in mind, let’s talk about the second case in which the doctrine
of blockchain immutability has been used to ridicule ideas. Here, we’re
referring to Accenture’s idea of using a chameleon hash  (
http://www.coindesk.com/absolute-immutability-will-slow-permissioned-blockchain-progress/)
to enable a block buried deep in a chain to be easily replaced. The primary
motivation, as described by David Treat (
https://www.accenture.com/t00010101T000000__w__/es-es/_acnmedia/PDF-33/Accenture-Editing-Uneditable-Blockchain.pdf)
, is to allow an old problematic transaction to be quickly and efficiently
removed. Under the scheme, if a block substitution does occur, a “scar” is
left behind which all participants can see. (It should be noted that any
later transactions that depend on the deleted one would need to be removed
as well.)"

Does anybody know if there is an implementation or at least description of
"chameleon hash" and protocols based on them?

Thank you!

-- 
SY, Dmitry Belyavsky
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