Tagged Base64

User-oriented format for binary data. Tagged Base64 is intended to be used in user interfaces including

• URLs
• Text to be copied and pasted

Tagged Base64 does not require additional encoding, such as quoting or escape sequences. Truncation and other forms of corruption can be detected with an integrated checksum.

To reduce confusion, the values are prefixed with a tag intended to disambiguate usage. Although not necessary for correctness, developers and users may find it convenient to have a usage hint enabling them to see at a glance whether something is a transaction ID or a ledger address, etc.

For example,

TX~QmVhdXRpZnVsEA
LA~SG9tZbo

Like the base64 value, the tag is also restricted to the URL-safe base64 character set.

Note: The tag may be omitted, but the base64 value cannot because it contains the checksum.

Standalone Executable

The crate includes a standalone executable for converting to and from Tagged Base64. See tagged_base64 --help for usage.

Rationale

Large binary values don't fit nicely into JavaScript numbers due to range and representation. JavaScript numbers are represented as 64-bit floating point numbers. This means that the largest unsigned integer that can be represented is 2^53 - 1. Moreover, it is very easy to accidentally coerce a string that looks like a number into a JavaScript number, thus running the risk of loss of precision, which is corruption. Therefore, values are encoded in base64 to allow safe transit to- and from JavaScript, including in URLs, as well as display and input in a user interface.

Prerequisites

In addition to the typical Rust development tools, wasm-pack is needed. The Makefile includes a setup target to install wasm-pack.

The Wasm tests require Firefox and Chrome to be installed.