What are multihashes that start with XL?

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1

From @JustinDrake on Wed Nov 23 2016 14:10:23 GMT+0000 (UTC)

The IPFS whitepaper use multihashes that start with XL. See example below

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What are XL multihashes?

Copied from original issue: https://github.com/ipfs/faq/issues/200

2

IPFS addresses are base58 encoded multihashes, so we can break it down like so:

$ echo XLZ1625Jjn7SubMDgEyeaynFuR84ginqvzb | base58 -decode | hexdump
0000000 11 14 de f8 ed 48 c7 8b 10 c7 84 6d 4f 60 a0 d0
0000010 d0 ee 95 65 a0 ca f5 ea 69 b0
000001a

This gives us the hex string 1114def8ed48c78b10c7846d4f60a0d0d0ee9565a0caf5ea69b0

From the multihash spec we see that the first 2 bytes give is the hash function and the length. The function id 0x11 indicates sha1 as the algorithm and 0x14 is the length (0x14 = 20 bytes = 160 bits = sha1’s standard length).