DHT lookup and SHA1

[john1deer]

IPFS supports multi-hash IDs for objects but in reality all hashes in the network are SHA2.

What happens if I decide to add an object or a node with a SHA1 (for example) ID? As the first bit would be different than about every other node currently on IPFS, the tree would be really skewed. Is that correct?

Does this mean IPFS supports multi-hashes in therory but not in practice?

[leerspace]

What happens if I decide to add an object or a node with a SHA1 (for example) ID?

The same thing that happens with the defaults, except for that SHA1 is used for the multihashes instead of a stronger hash function.

As the first bit would be different than about every other node currently on IPFS, the tree would be really skewed. Is that correct?

What do you mean by "skewed"?

Does this mean IPFS supports multi-hashes in therory but not in practice?

IPFS currently supports multihashes created using SHA1 just fine. Here's an example that works just fine for me using SHA1:

$ cat /dev/urandom | base64 | head -c 20 > temp
$ hash=$(ipfs add --hash SHA1 -q temp)
$ curl https://cloudflare-ipfs.com/ipfs/$hash