1
To receive funds, I was thinking of giving a user the option of displaying two QR codes:
p2phk e.g. 1AKDDsfTh8uY4X3ppy1m7jw1fVMBSMkzjPp2sh(p2wpkh) e.g. 34nSkinWC9rDDJiUY438qQN1JHmGqBHGW7Is it safe to only give them the option of receiving to a "compatibility" address?
5
Displaying two would be justified if you were asking about a BC1 p2wpkh vs a 3xxx p2sh(p2wpkh) because not everything supports BC1 but its pretty good to use when supported.
Displaying two isn't useful between p2pkh/p2sh as you've asked about because p2sh is supported everywhere and many wallets and services have used p2sh exclusively for a long time.
Supporting plain p2pkh is not something I'd recommend a new wallet bother doing. That development and testing effort would better be spent on newer functionality.
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Is it safe to only give them the option of receiving to a "compatibility" address?
Yes. All modern wallet software understand P2SH and can create transactions that send to such addresses.
What's the implication of displaying both? i.e. for a single compressed public key, you'll have utxo associated with multiple addresses (if people send to both.) – Malone – 2019-02-28T19:41:59.367
A UTXO is only associated with a single encumberment (script) - The fact that one private key controls multiple outputs is irrelevant. However, you should be using HD wallets to derive keys for BIP44/49/84 following standard paths, in which case they private key will not be common. – Raghav Sood – 2019-02-28T20:00:06.437
@RaghavSood So even if the address to be generated is p2sh(p2wpkh), I should derive from the HD wallet at say, m / 84' / 0' / 0' / 0 / 0? – Malone – 2019-02-28T20:07:42.003
1Actually I just noticed bip49 refers to this particular example. – Malone – 2019-02-28T20:29:17.533