Internet applications suffer from the lack of proper identity management. TCP/IP was designed as a network of networks with the sole purpose of identifying machines and not their users. The rise of the web in the 90s favored the emergence of servers that concentrated user access and capitalized on stored data to the point of being today the identity providers of a significant part of humanity. . The GAFAMs implemented an identity layer above TCP/IP because there was none and we all missed it.

For about ten years now, the concern for the protection of personal data has become a major subject for policies and new paths have been opened up, such as in particular the concepts of Self Sovereign Identity (SSI) which allows everyone to have their data in the format electronically as is done for paper data. From our point of view, what is called web3 is today the culmination of these approaches, web3 is not just cryptos and finance, web3 is also the decentralization of data and perhaps even above all data. ..

The Altme wallet that we offer is a so-called “Universal” wallet. It is universal in that it allows you to manage in the same mobile application both your cryptos, NFT and your identity data. Identity must be understood in the broadest sense, this of course includes identity documents but also the personal data of our associative, cultural, professional and economic life. Altme is simply an electronic version of the wallet we’ve had in our pockets for years. A Universal wallet is ultimately very common. The Altme wallet is a new generation of wallet, it is likely that in the medium term other provider wallets will see the benefit of associating data with the transfer of assets. identity allows a third party to manage its risk in an exchange. Identity is essential in any economic system.

Web3 suffers like web2 from the lack of proper identity management. On the other hand, there are particularities which make SSI integration even more difficult:

  • The users of web3 applications are even less docile than those of internet applications. they are more concerned with the management of their data because decentralized finance has already done its work.

  • Web3 applications require on-chain data integration but the verifiable credentials we use in the SSI are off-chain by construction so we have to find solutions, tricks to make a bridge that allow both to use the technology provided by the blockchain while guaranteeing the protection of user data.

Altme Wallet is an universal Wallet

A universal wallet is a wallet that carries the private keys of its crypto accounts and the verifiable credentials of its decentralized identity.

A universal wallet can buy, transfer and receive cryptos and NFTs and also receive and present verifiable credentials and verifiable presentations to the W3C standard.


This also implies that a universal wallet supports both connection protocols with a dApp such as Beacon (or its walletConnect equivalent on EVM) and SSI protocols (WACI PEX, SIOPv2, …DIDComm,..).

Altme wallet is available on Apple Store and Google Play .

Altme Sandbox is a low code SSI solution

Altme Sandbox is a low code platform to generate issuers and verifiers. The platform is an open source project :

It makes it possible to verify qualified attributes of a Decentralized Identity or issue for instance a Pass in minutes without diving in complex Self Sovereign Identity (SSI) concepts and tools.

Access is free :

DID for universal wallet

We have chosen to use the DID method did:key for practical reasons.

It is a DID method which has numerous libraries and is today supported by the EBSI/ESSIF ecosystem. Other DID methods can be used, but it seems to us, on the other hand, that it is preferable to be relatively far from the DID methods which are deduced from the blockchains and which could leave the opportunity to confuse the private key of an identity with that of an account used for a transaction.

A description of the did key method is available here :

DID private key vs blockchain address private key

It seems to us for example extremely dangerous to use by simplification the same private key of a blockchain address to support a decentralized identity.

The obvious risk is to eventually have an immediate correlation between an identity document issued for a user DID and blockchain transactions.

For this, the choice we have made is to derive the private key(s) of our identity with a specific path different from that used for the crypto wallets. Currently we use the derivation m/44’/5467’/0’/0/x for the generation of identity keys which avoids any collision with that used for Tezos m/44’/1729’/0’/0/ x while keeping the same passphrase.

The proof of blockchain address ownership

It is a VC which is issued by the crypto wallet and whose subject is the identity carried by the wallet. Once presented to a verifier, it is a credential that has the signature of the two private keys.

From our point of view, this VC is one of the most important of the universal wallets because it makes it possible to establish a link between the credentials and the addresses of the transactions while guaranteeing the maximum protection of the user’s data.

If it is desired to verify that the owner of an address A1 is over 18 years old, the verifier will receive a VC/VP over 18 and a VC/VP which proves that the identity subject of the Over18 ( is indeed the owner of the address A1.

Give an Identity to your crypto wallet

Current crypto wallets like Metamask, Trust wallet, Ledger Temple wallet do not carry personal data. It is therefore extremely difficult to know the user who is carrying out a transaction. In some cases this can be a problem.

The use of processes such as the KYC carried out by the site of the platform responds badly to this problem for at least two reasons:

  • it reveals all of a user’s personal data to the operator

  • it is often impossible to ensure that the crypto address is indeed owned by the person performing the KYC.

To solve this problem, the Altme wallet offers the possibility of being associated with a crypto wallet if the latter supports the Beacon (Tezos) or Wallet Connect protocols.

This association is made without exchanging private keys by issuing proof of possession of the private key by the crypto wallet. The Altme wallet can therefore carry the verifiable credentials of the user of a wallet such as Metamask or Ledger, which then simplifies and secures the onboarding of this user on web3 platforms.

Hybrid dApp and Pure dApp

What we call a Hybrid dApp is an application that uses a back end to store information local to the application. A large part of decentralized game applications or NFT marketplaces are built on this model. In particular, a centralized database is used to store the data of users who are authenticated by their blockchain address when synchronizing the wallet with Beacon for example.

What we call a Pure dApp is an application that has no back end. Many DeFi applications work on this model. The particularity of this architecture is that it is not possible to keep information from a user (VCs/VPs or verification result) locally and therefore it is necessary or efficient to have an on-chain storage.


The Verifier is the module of an application or an application whose purpose is to control the accuracy and origin of Verifiable Credentials / Verifiable presentations of a user (Holder).

The protocols supported by the Verifiers are the subject of numerous documentation in the repositories of the DIF and in those of the SSI ecosystems. In our case we opted for the use of Verifiable Presentation Request (w3C draft) or SIOPv2. The simplest use cases of a Verifier consist in validating that a user has the necessary credentials (Over 18 or Over 13 to access a marketplace, KYC/AML to access a DEX, etc).

It is therefore relatively basic information that is generally called a “verification result” and which is then transferred to the dApp. This information contains very little personal data of the user but on the other hand it is possible that the Verifier received and stored to carry out its process a greater number of information.

For this reason in particular, it seems to us that the Verifier must remain an external and independent service.

The multi-criteria approach makes it possible to deal with complex use cases involving several criteria. An example is that of a voting application that would like to whitelist only users who live in a specific city and who are, for example, under 25 years old.

Data persistence and on-chain storage : Whitelist vs Soulbound

In an SSI environment, the user carries their data in their wallet. At each onboarding he is able to present his VCs. Universal wallets have here a very big advantage over crypto wallets which can only hope that another dApp has previously created an on-chain record to mark an address as verified.

On the other hand, the question of data persistence arises for asynchronous actions such as that of an NFT drop or an ICO conditioned by a minimum subscription. In this case it is necessary to keep a list of addresses that have presented themselves beforehand, sometimes several weeks before the action.

For a hybrid application that has a base on a server, the implementation is simple. For a dApp you need a storage alternative.

This is where blockchain comes into play in the interaction of SSI and web3. VCs are inherently off-chain as they protect user data and regulations in many countries now include the right to be forgotten. It is therefore not possible to have a copy of a chained VC. It seems to us that even a “verification result” is already personal data that should not be exposed on chain. The choice we have made is to use whitelists or Soulbound tokens created at the start of the application (and financed by the application and not the user).

The question that arises is the use of data from a verifiable credential by a smart contract :

  • A whitelist is managed by a smart contract which allows to create whitelists adapted to each use case and then to add the blockchain addresses of the users of the service. It is created at the same time as the verifier. It must be able to be consulted by a smart contract of the application. Checking it updates the whitelist.

  • A non-transferable NFT (soulbound) is mined by the Verifier. The NFT is then validated by the smart contract with the creator address (Verifier address).

The verifier pays the transaction fees and the verifier’s DID must be known to the wmart contract to validate the forwarding address. The whitelist is managed by a smart contract that allows you to create whitelists adapted to each use case and then add the blockchain addresses of service users.

Verifier pays the fees of the transaction.