The MD5 twystlet is a pure Java implementation of RFC 1321 originally created in a fit of pure masochism for the memory and performance constrained environment of a mobile phone. The code is conservatively optimized using:

• in-lined method calls and constants
• unrolled loops
• careful allocation of local variables
• byte-code 'tweaks'

to give a high performance implementation in a much reduced footprint.

The implementation includes 3 variants:

1. A 'minimal' Java implementation that implements only the necessary functionality.
2. A hand-optimized byte code implementation that offers the same performance as (2) in a slightly reduced footprint.
3. A hand-optimised byte code implementation that offers the smallest footprint at the expense of reduced throughput.

The download [signature,key] includes:

• Full source for all implementations.
• Pre-built class files.
• JUnit validity tests.
• Japex performance test drivers.