How reliable is the adler32 checksum?

md5 checksum data-consistency adler32
Samuel Lampa picture Samuel Lampa · May 18, 2011 · Viewed 18.2k times · Source

I wonder how reliable the adler32 checksum is, compared to e.g. md5 checksums? It was told on wikipedia that adler32 is "much less reliable" than md5, so I wonder how much, and in which way?

More specifically, I'm wondering if it is reliable enough as a consistency check for long-time archiving of (tar) files of size 20GB+?

Answer

Schedler picture Schedler · May 18, 2011

For details on the error-checking capabilities of the Adler-32 checksum, see for example Revisiting Fletcher and Adler Checksums. Maxino, 2006.

This paper contains an analysis on the Hamming distance provided by these two checksums, and provides an indication of the residual error rate for data words up to about 2^11 bits. Which, obviously is much less than your requirement of 2^38 bits...

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