Bech32 conversion to legacy P2PKH?

Electrum now generates Bech32 addresses for SegWit wallets.

Example: bc1qnntcclssmtuvfw2te7q49lzvw67cfvpzxger4j

Pubkey: 023f1b3421c6ae0c1758834d40806c2418194b507be261fa343a0636653f3ec75b

If I search for that Bech32 address on btc.com, I get redirected to: https://btc.com/1FJJdX5g1DX7FRxJBhJNTDrRjTeihhsJLs

This pubkey-to-address tool also generates the same address from the above pubkey.

Is it safe to receive funds at this 1FJJd... address?
Is there a downside to using this rather than Bech32?

Jonathan Cross

Posted 2017-11-08T02:12:27.660

Reputation: 1 130

Answers

Is it safe to receive funds at this 1FJJd... address?

Kind of. Your wallet knows the private key that corresponds to that address as it is the same private key for the bech32 address. However it does not necessarily know that it should be looking for coins sent to this address, so any transactions that send coins to that address may not appear in your wallet and thus it will be harder for you to spend those coins.

Is there a downside to using this rather than Bech32?

As I said earlier, your wallet may not know about that address and thus won't track it. Even if it does, it is better to use the Bech32 address as that means that you will be using Segwit. The transaction fees for a spend from a segwit address will be lower than a similar spend from the non-segwit version of that address.

Andrew Chow

Posted 2017-11-08T02:12:27.660

Reputation: 40 910

9"Harder to spend" may translate into "lost" if for example the key is on a hardware device that does not support signing for the converted address type. – Pieter Wuille – 2017-11-08T02:52:10.377

Also bech32 support is not currently as widespread so it won't be usable in all the same situations as the legacy address – MeshCollider – 2017-11-08T02:52:11.083

@MeshCollider Yes, this is why I was exploring ways to convert Bech32 address to a form more widely accepted as "valid". Other wallets like Trezor use SegWit embedded into P2SH which works almost everywhere. – Jonathan Cross – 2017-11-08T13:03:49.907

Isn't the purpose of P2PKH addresses (starting with 1) to inform the software of the scriptPubKey used? If I get that correctly, then it would be highly unexpected for a wallet to look for P2PKH-type outputs derived from a bech32 address, as the latter is intended to be used with P2WPKH/P2WSH outputs. – FMCorz – 2018-02-01T15:11:43.713

1@FMCorz Yes. But the data encoded in a P2PKH address could be re-encoded as a P2WPKH address. But as you said, wallets won't expect that. – Andrew Chow – 2018-02-01T15:45:48.863

You can’t assume that any given software will be know to go searching for arbitrary encodings of the public key you’re “converting” to. Depending on the wallet software on the other end, your payment will likely to be missed or at worst lost entirely in the case of a hardware security module that can’t be altered.

There's no situation in which you should ever need to be doing this.

Anonymous

Posted 2017-11-08T02:12:27.660

Reputation: 10 054