Support for variable-length hashes

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
55/100
Issue type
Feature
Clarity
Clearly specified
Activity status
Stale
Tech stack
java
Domain
cryptography

Research direction

Start in Multihash.java at the constructor and deserialize/fromHex call path shown in the stack trace, then reproduce the failure with Multihash.fromHex("18028eb4"). Done means the SHAKE128 example with a 2-byte output is accepted instead of raising the fixed-length exception, while the existing deserialization path continues to work.

Written by the indexing model from the issue text.

Description

Some algorithms (such as SHAKE128) can generate an output of arbitrary length. For example, the following are all valid SHAKE128 hashes of the string hello in UTF-8:

8eb4
8eb4b6a932f28033
8eb4b6a932f280335ee1a279f8c208a3
8eb4b6a932f280335ee1a279f8c208a349e7bc65daf831d302

(generated by the online hash calculator)

In particular, this code should work:

Multihash m = Multihash.fromHex("18028eb4");

Whereas it currently fails with this exception:

java.lang.IllegalStateException: Incorrect hash length: 2 != 32

	at io.ipfs.multihash.Multihash.<init>(Multihash.java:162)
	at io.ipfs.multihash.Multihash.deserialize(Multihash.java:218)
	at io.ipfs.multihash.Multihash.deserialize(Multihash.java:223)
	at io.ipfs.multihash.Multihash.fromHex(Multihash.java:273)
Dominant language
Java
Stars
53
Forks
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