Today we are excited to release our solution to conveniently send cryptocurrency to any email address.

To start sending bitcoin to any email address, simply head to . On this page, you can choose the amount and crypto you want to send, together with the other person’s email address and your signature and email. We use this information to keep you up-to-date with the status of your payment by email.

After filling out your details and clicking “Review Payment”, you can review the information you provided. On this page, you can find the secret unlock code that we will email to the other person.

After confirming your details, LockerX starts creating your smart contract and locking it so that only the other person can unlock it using their secret unlock code. When the contract is locked, you’re asked to send your bitcoin payment to it, at this point only the person with the secret unlock code can withdraw the funds. After you deposited your crypto, LockerX emails the other person to inform them of your payment.

The other person simply has to visit the link LockerX sends them to claim their payment.

After filling out and reviewing their information, they will receive the payment to their wallet. That’s it!

If you noticed you made a mistake, for example you sent the wrong amount or used the wrong email address, you can easily cancel the payment and send the crypto back to your account.

If you want to learn more about Flash Locker and see all available options, visit the Flash Locker documentation page .

How Flash Locker works

Flash Locker works by tokenizing your Bitcoins on the Stellar blockchain. When you deposit your Bitcoin into the Flash Locker, we issue a token on Stellar for the equivalent amount of Bitcoin, this token can be redeemed for the same amount of Bitcoin. The Flash Locker Stellar account is locked so that only users with the secret unlock token can use it. In more technical terms, we set the signer of the Flash Locker account to the hash of the unlock token.

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Today we introduce a new service to bridge cryptocurrencies to the Stellar network.

As an anchor, we will keep your cryptocurrencies safe and, at the same time, we will issue you an equal amount of that cryptocurrency token that you can use on Stellar, taking advantage of Stellar fast and cheap transactions.

We like the transparency and auditability that blockchains provide, for this reason we decided to link every deposit and withdrawal by storing their hash in the Stellar transaction.

For example, this transaction that issues 0.1 Bitcoin Cash contains a memo that links the transaction on Stellar with the transaction on the Bitcoin network . Because of this, the circulating supply of our tokens can be independently audited by everyone, ensuring everyone can trust it.

At launch, we support the following cryptocurrencies, with plans to expand to include more cryptocurrencies in the future:

  • Bitcoin
  • Bitcoin Cash
  • Litecoin
  • Dash
  • ZCash

Are my funds safe?

Yes, your funds are completely safe and can be redeemed at any time. We store your cryptocurrencies in an industry-leading multi-signature wallet service.

All our tokens are backed 1-to-1 by cryptocurrencies, you can check this by monitoring our issuing account . Every transaction contains the hash of the deposit transaction to link the two transactions together.

Getting started

You can get started by visiting , we provide an easy-to-use interface to deposit and withdraw funds to and from the Stellar network.

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One question that often comes up when building smart contracts is how to attach documents to them. For non-technical users, attaching documents to payments is a feature that is taken for granted. After all, if you look at your email inbox you will almost surely find an invoice attached to each of your payment confirmations.

Attaching documents to blockchain transaction is not simple, the main problem is that documents (especially PDF documents) can be huge compared to the size of a transaction sent to the network. Blockchains are designed to store transactions that are a few bytes in size, not documents that can weigh several megabytes!

Another issue is that the data on the blockchain is visible to everyone, this is great from a transparency point of view but documents may contain sensitive information that we are not willing to share with the world. This poses an additional challenge since we may want to prove the existence of a document (for example, an itemized invoice) while at the same time keeping the content of the document private, to be shared only with trusted parties.

You can use a service like LockerX to create smart-contract transactions that also include document attachments, without being an expert yourself. In the next section, we will describe how we implemented document attachments in LockerX.

Hash it!

As mentioned in the previous section, the challenge in attaching data to blockchain transactions is the limited amount of storage space and the need to keep documents private. Luckily, both problems can be solved with the same tool: hash functions!

Hash functions are mathematical functions that map data of different sizes (for example documents) to values of the same size. Cryptographic hash functions are hash functions with some additional guarantees:

  • Given a hash value, it’s infeasible to generate a message that produces that hash value,
  • It’s infeasible to produce two different messages that have the same hash value, that is the function is collision-resistant,
  • A small change to the message produces a completely different hash value.

Link your document

Computing the hash of documents it’s not enough, we also need to make sure this data is included on the distributed ledger. Storing the hash on the ledger is important because it proves that the data itself existed at the time the ledger was computed:

  • Blockchain ledgers are immutable. Storing a hash value in a ledger is enough to prove that we had that value at the time since it is impossible to retroactively change a ledger.
  • The document was not altered in any way. Since any small change to a document produces a completely different hash value, then if the document produces the same hash value that is stored on the ledger it means it was not modified in any way. Additionally, since it’s infeasible to have two documents produce the same hash value, then the document must be the same as the original document.

One last question is where to store the document itself since only its hash is stored on the ledger. The answer to that depends on your use case and how private your document is. Publicly available documents can be stored unencrypted on distributed file systems such as IPFS, while private documents should be stored encrypted and only shared with trusted parties.

On LockerX, documents are stored securely by us and are shared only with the parties you give access to.

Why not give it a try?

In this post, we described a strategy to use blockchain to prove the existence of a document at a given point of time. If this sounds exciting to you, make sure to check a live version of these ideas on LockerX.

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