<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi,<div class="">The probability of collision with MD5 is more compared to SHA256 based message digests. Even SHA128 is not strong enough and most dedupe engines use SHA256 based message digest.</div><div class=""><br class=""></div><div class="">Obviously if there is a collision, the incremental backup may not capture modified data which result in corrupt data backups.</div><div class=""><br class=""></div><div class="">Murali Balcha</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Apr 11, 2017, at 3:52 AM, <a href="mailto:yuliyang@cmss.chinamobile.com" class="">yuliyang@cmss.chinamobile.com</a> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span class=""></span>hi,all</div><div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""> why we use sha256 instead md5 in chunk based backup-driver , in the current file chunkeddriver.py, we have <span style="background-color: rgba(0, 0, 0, 0); font-size: 10.5pt; line-height: 1.5;" class="">object_sha256['sha256s'] list to store all the sha256 value of</span><span style="line-height: 1.5;" class=""> </span><span style="orphans: 2; widows: 2; line-height: 1.5;" class="">sha_block_size data , why we do not use md5 ,md5 is faster compute than sha256,and we all use the md5 value in </span><span style="background-color: rgba(0, 0, 0, 0); font-size: 10.5pt; line-height: 1.5;" class="">_backup_chunk too, so we just need to compute one time and used in two diffrent place,it save much time</span></div><div style="font-family: Helvetica; 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