Data security in BitDust system is based upon crypto-system with an open key. For data encryption and digital signature creation this asymmetric algorithm uses a key consisting of two parts: public key and private key. It is a secret key and only this key protects authenticity and user's personal data.
The private key is created by the first BitDust program start. The original key is stored on the hard disk drive in the folder
On each start of BitDust program the key will be loaded into the operational memory of the computer and will be used for user data protection. After program stops, this temporary copy of the private key will be automatically deleted during the memory cleaning.
It is highly recommended to make several backup copies of the key, record it on different media and hide in safe places just after secret key generation. These could be USB-flash card, CD-disk, A4 paper sheet or encrypted file on another machine. Only this secret key gives an access to user data! By its loss all your information will be completely lost.!!! Never do copies of the key thru open or untrusted channels! The reliability of your personal information security is completely dependent on the private key safety.
The scheme of two-way user authentication in BitDust network is described in the section User Identification.
Public part of user key or, in other words, "open" key is stored in identity file which is open for everyone and serves as a kind of user passport. These files can be freely allocated in the Internet and have unique address – IDURL.
Public key is used for encryption of incoming data which need to me transmitted via Internet from remote machine to machine of the user himself. Only with the help of a secret key which is stored only in user’s machine you can decrypt the data.
Thus public key must be forwarded to all the nodes with which you want to maintain a safe connection. For this purposes BitDust program has a functional for distributing identity user files to each other.
All user identity files are secured with digital signature. By creating or changing user identity the generation of an digital signature takes place – it is connected to the file content and serves for security from changes.
Digital signature is calculated due to the file content via Hash-function, for this one needs to have a private user key which is stored only on his machine. Thus only the user himself has a possibility to make changes to the publicly available "passport" and only when having his secret key on hands.
The general principle of user identity protection from changes is based on the fact that all other nodes check the correspondence between digital signature and file content each time when they receive a new copy of its identity – this standard method in cryptography is called VerifySignature.
Digital signature is used not only for protection of user identity file from modifications but also all service data which are forwarded from one node to another in the BitDust network.
All users exchange so-called "service packages", which include digital signature and are safe from modifications in the process of forwarding in the Internet. This enables data dibbling security as all received packages will be checked for the correspondence of content and digital signature.
Service packages are forwarded in the not encrypted form and still can be marked as signed packages. The structure of a signed package is the following:
Command– BitDust protocol command name
OwnerID– package owner IDURL
CreatorID– IDURL of the creator, whose key signed the package
PacketID– package identifier
Date– creation date and time
Payload– useful data in source (not encrypted) form
RemoteID– IDURL of addressee
Signature– digital signature
To hide the data another class of packages is used, it is called "encrypted block".
These data blocks are forwarded inside the service packages and the field
Command will have a value "Data" – which means that the given package contains encrypted data block.
You can represent this mechanism as two layers where internal encrypted layer is somehow "put" inside the external one – or the service one:
The structure of encrypted block is the following:
CreatorID– IDURL of data block creator
BackupID– data identifier
BlockNumber– block number in the chain
SessionKeyType– algorithm used for encryption
EncryptedSessionKey– encrypted session key
Length– actual length of not encrypted data in that block
LastBlock– last block in the data chain marker
EncryptedData– encrypted useful data
Signature– digital signature
At the moment the encryption of data recorded in the field
EncryptedData is done by the DES3 algorithm.
This symmetric algorithm uses so-called session key for data perturbation – anyone who knows the key can decrypt them. Session key is generated for each new data block and is used for encryption of only this block. Data security is based on hiding the key itself – it is encrypted with the help of receiver’s public key. As the result to the structure of the encrypted package get not the session key itself but its encrypted copy, which is recorded in the field
EncryptedSessionKey. Encrypted data are recorded in the field
Thus RSA algorithm encrypts only session key, but the data themselves are secured with DES3 algorithm. Such an approach allows increasing BitDust program performance, as the symmetric method of encryption DES3 works much faster than algorithm RSA. In other words the simple combination of two algorithms is used:
We are looking forward to adding a support of AES3 and BlowFish algorithms and give users a chance to choose desired method of symmetric encryption in the program settings.
Session key is not available to anyone except for the user himself – he and only he can decrypt the field
EncryptedSessionKey with the help of the private key and extract the session key. Thus user data which get to supplier’s machine are kept in an encrypted form and they are not available for reading to the supplier.
Supplier receives data portions inside service packages, in the field
Payload, and records the data completely to different files on his hard disk drive. As a result the encrypted block portion are allocated on the supplier’s node – the field
EncryptedData is kept the same as it was when created on the machine of data owner.
When user requests his data back from supplier’s machine they are back in the source encrypted form, but again wrapped in the service pack structure for change security. Then the user decrypts field
EncryptedSessionKey (with his private key) and extracts from there the session key, which then decrypts the source data block from the field
You can upload some data into BitDust network and immediately remove the source file from your computer - now only you can restore it again using your Private Key. Since that moment, exactly same file (or its copies) is no longer exists in our Universe!
The information uploaded to the BitDust network loses its integrity, as each supplier allocates at his machines only encrypted blocks. Nodes storing your data can be identified, but they are located in different part of the World and read your data is possible only by using private kry.
One may talk of uploaded in the network data going through the process of "data disintegration" – become absolutely useless for everyone except for the data owner himself. Only he having the private key can reassemble them providing having the baseline minimum quantity of fragments in each block.
The given fact allows storing data of any sensitivity level in the BitDust network, as only the owner of data has an access to it.
In addition to a possibility of storing your data distributed on the remote machines, BitDust project offers another, absolutely unique possibility to have a total control over your distributed space and secure the data from theft or elimination.
It is possible to organize the fully secured storage of user data so that it will be absolutely unavailable for anyone apart from the owner. He and only he will have the key to the only existing copy of these data, allocated on the multiple machines in BitDust network. These nodes store only encrypted fragments of the general data array and cannot read them or use them in any way.
It is okay to just delete the original file from the disk drive after the data upload to the BitDust network has been finished. The private key user can store on a USB-stick, and a local copy of the private key can be deleted from local disk. BitDust program will be started on the given computer only if this USB-stick is plugged in and software will read the secret key by the start and store it in computer operation memory, without creating a copy on the local disk drive. Now, after launching the program the user extracts USB-stick and hides it in a safe place. So USB-stick acts as a normal "physical" key - just like a key for your car.
Let us suppose that the user has lost physical control over his computer due to its theft, or any other reason. To keep the total control over his data user needs to be sure that computer power source was turned off – in most cases it is easily can be done with additional hardware devices/sensors installed on your laptop.
By doing this you can be sure that the copy of secret key which was left in the operation memory of your computer was erased. Afterwards the only private key copy is left with the user’s USB-stick and the access to his personal data is possible only to him. So user just need to download BitDust program again on another computer, insert USB-stick, and restore access to his data. Because data still was kept on his suppliers securely!
In addition to portative USB-stick we recommend you to print the private key on a regular A4 paper list and keep it in the safe place. In this case the user provides additional security if the USB-stick gets broken for example. We also advice you to put a password and encrypt your private key stored on USB-stick, so that even if you lost it you are still safe.
This approach enables practically the same common mode of operations with data, which are usually stored at a cloud server, for example, but gives a significantly higher level of control over them. As data stored at cloud servers are under control of service suppliers, even if it was encrypted on client side. Indeed, data can be encrypted by the user before he put it on the cloud server. Still the data is stored in data centers in an integrated form and can be read (in most cases it is still not encrypted), deleted, taken away without notice. Another aspect here is that access/traffic to your customer account can be monitored by service provider in real time - they will know exactly when, who, and which file was uploaded/downloaded.
The given approach is unique, after uploading personal user data in the BitDust network and deleting original data from the local hard disk drive of the computer no physical integral copy of the given piece of data exists on the Earth. Data stored distributed on remote computers are just fragments of source data and they are useless if taken separately – they undergo a process of "data disintegration". Restoring the source user data is possible only with the help of the private key which is kept on user’s USB-stick or possibly on additional media.