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The NEM team would like to thank Aenima (Telegram: @Aenima86) for making this project and blog.

The recovery of keys is a big challenge in all cryptocurrencies. One of the main concerns for many people using cryptocurrencies is the security of their funds. This is not an easy task for most people because we are used to centralized organizations taking care of security and supporting us when we have forgotten our password. In crypto-land, our funds are forever lost if we lose our keys or in some cases, third-party services have scammed people stealing all their crypto coins. This is why a Key Recovery Service (KRS) is highly relevant for the adoption of a cryptocurrency such as XEM.

While completely functional, we are releasing this product as an Alpha proof-of-concept. Please use after auditing the processes and code. We also recommend downloading this program and running it locally.

The KRS is built around three use cases:

  • Create new KRS: the creation of new private keys, which can be recovered if lost.
  • Encrypt existing KRS: recovery service for existing private keys.
  • Multisig KRS: a user wants to use a third-party service (e.g., a wallet), but wants to make sure he can access his funds if the service shuts down, he forgets his password, or he loses faith in the service.

Create new KRS

The create new KRS idea comprises that the user uses the KRS service to generate a private key. The key is generated based on a random seed + personally identifiable information. Furthermore, a unique webhook is generated – this can be stored without high security (e.g., in email or notes) because the webhook can only be activated to restore the keys in combination with the personally identifiable information (which should only be known to the user).

KRS

The user can choose which personal and secret information he wishes to use, for example, this could be information about the title of his favorite book in combination with his passport number and his credit card number; this is information which is only known to the user creating the keys. The KRS service is all browser based, which is important for security because no information is leaving the user’s own computer. Subsequently, the user’s new private key is calculated and can be imported into the user’s wallet. Furthermore, a unique link is created which the user can store in a non-secure manner, and can be activated for a key recovery.

Encrypt existing KRS

Additionally, an existing private key can also be linked to the key recovery service. The private key is encrypted using strong encryption methods and a random seed in combination with personally identifiable information. Like the create new option, a unique webhook is generated, and this can be saved and later used for restoring the original key using the personal information.

KRS

Multisig KRS

A major problem wallet users encounter is the security of the keys. While most new secure wallets (in the crypto world) implement multi-signature, in which 1 or 2 keys are created and stored by the user, a problem arises when the user forgets one of the passwords as they would then lose access to the wallet and its contents. The idea with a 2-3 multi-signature wallet where the user controls 2/3 keys and the service 1/3 is important because the user is in control and his fund cannot be compromised in case the service is shut down, get hacked, etc.

KRS

The multi signature KRS tries to deal with creating 2-of-3 multisig accounts and the problem of recovering lost keys. The idea pretty simple in theory. The user provides a private key with enough funds for a multisig conversion fee. Then the KRS creates the 2-of-3 multi signature account where one key can be stored by the user, one key can be stored by the service and one key by the KRS. This is not entirely true, because the KRS doesn’t store any keys, but the user is provided with a unique link which can be activated along with the personally identifiable information for recovering the last key. The KRS is open source which means that anyone could run the service and the user could in principle use any of these providers to recover his keys.
KRS demo

Check out the DEMO. (tested in Chrome 59.0.3071.115, pulling code from github)

or

the github: https://github.com/aenima86/NEMkrs

Constructing recovery key

The KRS uses the NEM-sdk for core functionality. One important aspect when dealing with crypto-keys is that they are created with the proper randomness in order to be safe. The random seed is created using the random bytes function when the website is loaded.

// Load nem-browser library
var nem = require("nem-sdk").default;  
// Create random bytes from PRNG
var rBytes = nem.crypto.nacl.randomBytes(32);  
// Convert the random bytes to hex
var randomSeed = uaConv(rBytes);  

To calculate the recovery private key, the random seed is combined with the personal identifiable information provided by the user. Besides the private key, a webhook containing the random seed and the question selected by the user is constructed.

. . . index.htm?seed=5afcfa29c6bd34b5e9830360665559f278b8bcaa2ad0e93141023fd07dc1895d&Q1=Your%20national%20identification%20number?&Q2=Your%20date%20of%20birth?&Q3=Your%20pasport%20number?&Q4=Your%20e-mail%20address?

By activating the webhook the user can reconstruct the answers and the KRS can in combination with the random seed recover the private key. This method is smart because the user does not have to trust a KRS service for storing his private keys.

Converting to multisignature account

For the multisig 2-of-3 KRS we need the user to provide a private key for the account to be converted. The account needs to hold enough funds to pay the fee for converting to a multi signature account and activating the new keys (a total of ~5 XEM on the testnet). Before we convert the account, we need to create three new private keys; the first two keys are created by pure randomness:

// Create key 1
var rBytes1 = nem.crypto.nacl.randomBytes(32);  
var privateKey1 = nem.utils.convert.ua2hex(rBytes1);  
var keyPair1 = nem.crypto.keyPair.create(privateKey1);  
var publicKey1 = keyPair1.publicKey.toString();  

The last key is created in the same manner described for the single key KRS. This key is hidden from the user but can be recovered using the webhook with the random seed and the questions. The three new keys are activated by sending a 1 XEM + fee from the multisignature account to each of the new keys and back again.
Now that we have the private keys and corresponding public keys for the three keypairs (+ the private key provided by the user) needed to convert the multisignature account, we do this by broadcasting a multisig transaction to the network.

Assuming we want to convert Johns account with the public key:

  • Account 'John' public key: a1aaca6c17a24252e674d155713cdf55996ad00175be4af02a20c67b59f9fe8a

Into a 2-of-3 multisig account meaning the account has three cosignatories and at least two cosignatories have to sign to complete a multisig transaction

  • Cosignatory 'Key 1' public key: 6083df7119d43e815ed2967c795f806f6b73f8f92a56a7611e3848816ec50958
  • Cosignatory 'Key 2' public key: 0662ed29cbfa7038530fb7f52df865eed6708d51bc7a24bcd05db35185b53c70
  • Cosignatory 'KRS Key' public key: cc61676a4275abcffd10a9ea1081091ff054a1a8a720429256aebf8034aab099

We would have to create a JSON object that looks similar to this (test network):

{
        "timeStamp": 9111526,
        "fee": 28000000,
        "type": 4097,
        "deadline": 9154726,
        "version": -1744830462,
        "signer": "a1aaca6c17a24252e674d155713cdf55996ad00175be4af02a20c67b59f9fe8a",
        "modifications": [
        {
        "modificationType": 1,
        "cosignatoryAccount": "6083df7119d43e815ed2967c795f806f6b73f8f92a56a7611e3848816ec50958"
        },{
        "modificationType": 1,
        "cosignatoryAccount": "0662ed29cbfa7038530fb7f52df865eed6708d51bc7a24bcd05db35185b53c70"
        },{
        "modificationType": 1,
        "cosignatoryAccount": "cc61676a4275abcffd10a9ea1081091ff054a1a8a720429256aebf8034aab099"
        }
        ],
        "minCosignatories" : {
        "relativeChange": 2
        }
}

After the transaction is signed and is accepted by the network by including it into a block, then John's account is now a 2-of-3 multisig account. From this point on, only the cosignatories can initiate a transaction for the John's account. Also, any transaction from John's account must be a multisig transaction. We recommend you create a new testnet account and use the test net faucet to get some xem to test this KRS.

We also remind users that this product is in Alpha proof-of-concept stage and while no known flaws exist in the creation of keys, it is recommended to be used only after auditing the code and processes yourself.

Credits

Author: Aenima

Icons made by DinosoftLabs & Freepik from www.flaticon.com, Creative Commons BY 3.0

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