south africa has launched a SMS service to send bitcoin without internet

[Saint-loup]

Technically it could be implemented in a more decentralized way with a little more effort which would also solve the security problem.

For example the user's phone could send a message to the centralized server with the user's address to first fetch a list of UTXOs. Then the user can locally build a transaction spending any of the given outputs, even sign it offline (for example on another device) and then send it back to that server through SMS.

The first contact could also act as a registration so that the server can associate your phone number with your address so that if anybody wanted to send you coins they send a message to that server with your phone number and get your address.

The only limitation I can think of is the SMS size which user may need to send/receive multiple ones per tx considering the size of the transaction could be bigger.

For the size limitation you could use MMS instead of SMS, and even send/receive QR code pictures through them.

I didn't test it personally so I don't know if it is working properly but Samourai wallet seems to offer a feature to send signed transactions to broadcasting servers through SMS. You won't get your last UTXOs not synchronized in your wallet if you don't have internet access, but it should allow you to spend the other ones at least.


https://www.samouraiwallet.com/offline
https://github.com/MuleTools/txTenna

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[pooya87]

You won't get your last UTXOs not synchronized in your wallet if you don't have internet access

By sacrificing a bit of security UTXOs can also be sent through the same system. The centralized company user contacts only has to send the "tx_hash + index + amount" instead of the whole transaction containing the output since the user already knows their own address (the pubscript and how to sign the tx). Consequently the amount of data per UTXO is reduced to 32+4+8=44 bytes.

[KingsDen]

One thing I always say about BTC is that, what we have today is not the finest version of bitcoin. We are still in the early stage of adoption of crypto industry. We should expect several changes in bitcoin and we should expect several bitcoin related innovations. This is to keep bitcoin up-to-date and make it dynamic to soothe divers human needs and methodologies.

We shouldn't kill ourselves because of security. Most times we over emphasize this security of a thing. We all have our simcards linked to service providers and connect to our local bank accounts where we have thousands and millions of dollars, how many times has the simcard being cloned and the money in your account emptied.
This might not be a secure way to send btc but just like the LN, it can help in sending Sats.

[negancoin]

"SIM cards as private keys?" This doesn't seem a good innovation where security is of utmost consideration.

No, your SIM card isn't used as private key. Phone number of that SIM card is used to login on their centralized service. But obviously it has different security concern.

It's not used a private key as of yet, but The article says he is looking for a way to use SIM cards as private keys because the current service works against the Bitcoin ethos of “not your keys, not your coins.”. Personality, I wouldn't trust anything that is controlled by the carrier to hold private keys.

[YOSHIE]

this is a SMS service which allows sending bitcouns with a text. Read the full article below

SMS is an old method used by many Bitcoin sending services, especially exchange services, but the rise of hackers and scams that take the path of sms / by tracking mobile numbers, many Bitcoin services currently apply the three-option method of email, authentication and sms.

The service method using sms is a less secure method, except as I said in a combination of three options, for that be careful sending Bitcoin through the sms service line, For this reason, currently Africa is one of the countries with fast crypto growth, many services in Africa use a more secure method of sending Bitcoins than SMS services.