About Tiles

General information about the Binary Transparency log for Pixel is available on the main Binary Transparency Page.

This page contains more details on the format of the files under the tile/ directory.

These files contain the hashes of the Merkle Tree nodes representing the Binary Transparency log for Pixel Factory Images. Furthermore, these hashes are packaged into tiles. For an overview of how splitting the tree into tiles see Tiling a Log.

In this log, the nodes are hashed using SHA256. We use the tlog library to write the tiles specifically with a tile height of 1. That means that each tile contains at most 2^height = 2 hashes, each of them 32 bytes.

Details of tile path constructions can be found in the tlog Tile docs. For example, let's take a tree of size 8. If you're looking at entry at index 3, it would be the first hash in tile t(0, 1). Paths for tiles are of the form tile/H/L/NNN[.p/W]. So, the path for tile t(0, 1) would be https://developers.google.com/android/binary_transparency/tile/1/0/001. The tree root would be in tile t(3, 0)/1, which is path https://developers.google.com/android/binary_transparency/tile/1/3/000.p/1.