On Thu, Jul 16, 2009 at 8:18 AM, Michael Tinsay<[email protected]> wrote: >> From: Rage Callao <[email protected]> >> >> 2009/7/13 Pablo Manalastas : >> >> > We can suggest to Comelec to compute SHA1 or MD5 checksums of the approved >> programs, and at election time, the checksums can be recomputed (manually) >> and >> if the original checksum and new checksum agree, then there is no >> substitution. >> >> >> AFAIR, SHA1 and MD5SUM have been broken. > > > While there is still the probability of collission, what is the possibility > that such can be used to "falsely validate" the data and programs that will > be used for the election? >
here is how digital signature works... for signing at precinct level... 1) ER = election return digital document 2) hashvalue = MD5_or_SHA1(ER) 3) signvalue = ENCRYPT(hashvalue, privatekey) send ER + signvalue to comelec server... the signvalue above is the encrypted hashvalue of ER document using the signer's privatekey.. signvalue is now the digital signature of ER document... for validating or verifying at canvasser level... a) hashvalue1 = DECRYPT(signvalue, publickey) b) hasvalue2 = MD5_or_SHA1(ER) c) compare hashvalue1 to hashvalue2.. if equal then authentic... otherwise bogus.. as you can see... hash function or message digest such as MD5 or SHA1 is not important here and whether it is collision prone or not for sending ERs... what important here is the privatekey encrypting the hash value of ER documents... once a cheater got a copy of BEI's privatekey without passphrase protection... he can create its own ER and signs it... take note also for manual election.. vote buying was rampant.. for automated election.. privatekey buying is going to happen aside from vote buying :-> but for smartmatic program to test its authenticity... we need a higher message digest such as SHA2 family (eg. SHA256, SHA384, SHA512) to avoid collision as the comelec is the one signing smartmatic program... they can create another program (the cheated one) padded some bytes just to have the same hash value with the orignal program (collision) and signs it... fooler. _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List http://lists.linux.org.ph/mailman/listinfo/plug Searchable Archives: http://archives.free.net.ph
