Bitzi Bitprint Definition

We take both the SHA1 hash of a file, and the "TigerTree" hash of a file. TigerTree is based on the Tiger hash algorithm, applied to each 1024-byte block of a file, then combined up through a binary hash tree to a final summary value. (See the Tree Hash EXchange format (THEX) specification for more details.)

Such a composited hash tree value allows compact proofs that file fragments combine to form the full file - a useful quality for verifying or resuming downloads-in-progress from unreliable peers, among other applications.

When transmitted or displayed, the raw bitprint is encoded using Base32, and a '.' (period) character is inserted between the SHA1 and TigerTree parts. For example:

QLFYWY2RI5WZCTEP6MJKR5CAFGP7FQ5X.VEKXTRSJPTZJLY2IKG5FQ2TCXK26SECFPP4DX7I

Sometimes, if this value needs to labelled as a distinctive name for the underlying file in a standard manner, the value will be preceded by "urn:bitprint:", like so:

urn:bitprint:QLFYWY2RI5WZCTEP6MJKR5CAFGP7FQ5X.VEKXTRSJPTZJLY2IKG5FQ2TCXK26SECFPP4DX7I

Further documentation of the bitprint and TigerTree conventions is forthcoming as an Intenet-Draft.