I'm working on a bitcoin signer App on iOS

It works compeletely offline. It does not store any infomation on the device. It supports multi-sig signing. Signing Steps: Scan PSBT from a wallet* and show info Read the key in NFC tag Sign with the key Cleanup the key in memory Show signed PSBT QRCodes to a wallet* wallet: watch-only wallets like Sparrow or Bluewallet Pros No data is stored in the App. So you can directly delete the App after using it before you turn off the airplane mode. The key only revealed in memory for a very short time. With the sandbox mechanism in iOS, it’s pretty much 99.99% safe. No vendor attack. iOS devices are public product and you can compile the code yourself. The whole process can be done in the Airplane mode. Multisig is supported to get better security. NFC tag is better to use than paper QRCode for seed. They are not noticeable by thieves and waterproofing. And the price is quite cheap, it is about $0.5 per NFC tag. The transaction information is more readable on iPhone’s big screen than hardware wallets. Cons You still need to keep the mnemonic words in case of the NFC tag broken. Although the data on the tag is protected by the Argon2 + AES256GCM SIV, there is still possibilities to do brutal force attack on the NFC tag data. But you can easily cover that with passphrase or multisig. It's already working on my devices on Testnet. Is anyone interested? submitted by /u/qdwang [link] [comments]

Jun 25, 2025 - 20:49

wallet: watch-only wallets like Sparrow or Bluewallet

No data is stored in the App. So you can directly delete the App after using it before you turn off the airplane mode.
The key only revealed in memory for a very short time. With the sandbox mechanism in iOS, it’s pretty much 99.99% safe.
No vendor attack. iOS devices are public product and you can compile the code yourself.
The whole process can be done in the Airplane mode.
Multisig is supported to get better security.
NFC tag is better to use than paper QRCode for seed. They are not noticeable by thieves and waterproofing. And the price is quite cheap, it is about $0.5 per NFC tag.
The transaction information is more readable on iPhone’s big screen than hardware wallets.

You still need to keep the mnemonic words in case of the NFC tag broken.
Although the data on the tag is protected by the Argon2 + AES256GCM SIV, there is still possibilities to do brutal force attack on the NFC tag data. But you can easily cover that with passphrase or multisig.

It's already working on my devices on Testnet.

Is anyone interested?