What encryption does Secure Phone use?

Secure Phone uses multiple different types of encryption for different purposes.Secure Email: PGP encryption with AES-256 cipher and RSA 4096-bit keys.Secure Chat: OTR protocol with AES-256, 4096-bit Diffie-Helman and SHA-256 hashing, and Double Ratchet Algorithm to ensure real-time encryption of group chats. It uses ZRTP encryption for voice-over IP (VoIP) calls.The protocols described above ensure that all communication remains encrypted from the moment it leaves the sender’s device until it reaches the receiver’s phone. (End-to-end encryption)Secure Vault: AES XTS encryption with SHA-512 hashing and full-disk encryption.

Are there encryption backdoors in your products?

No. The aim of our products is to provide maximum security of communications to ensure privacy and confidentiality. Creating intentional workarounds to the security they provide is at odds with that aim. A backdoor is a security flaw that could be used both with benevolent and malicious intent. Since we can’t afford the latter, we have not introduced any backdoors in our products.

How secure is PGP?

The security of PGP depends on the size of the cryptographic keys employed in the particular implementation. Our encrypted email app relies on 4096-bit RSA keys, which are beyond the scope of contemporary supercomputers – brute-forcing a key would take thousands of years even for a state-backed adversary. As long as attackers don’t get hold of your private key (which in our implementation is stored only on the user’s end), they cannot read the content of your PGP-encrypted emails.

Where are users’ PGP encryption keys stored?

Secure Email, our PGP email client, doesn’t rely on a public key infrastructure (PKI). The user’s encryption key pair (a public and private key) is created on the device when the user first starts the app. The keys are stored on the device, or can be exported – in case the user switches devices, or if they simply want to have a backup somewhere other than on their phone. The keys are always under the user’s control. We do not have copies of them on our servers.

What happens if I lose my PGP keys?

Unfortunately, if you lose your PGP keys, you will lose access to all messages that you have ever encrypted with them. We will not be able to help you, as we do not store backups of user keys on our servers. It is advised that you do so, at a location of your choosing.

How do you guarantee instant messaging is only peer-to-peer?

Secure Chat, our instant messaging app, sends messages only when the sender and the recipient are both online. Then the message passes through our server infrastructure – and gets deleted the moment it gets sent to the recipient (regardless of whether it gets delivered or not). This way we guarantee no messages ever lay dormant on our servers. Also, the messages stay encrypted during all steps of the process described above.

Can I delete messages after I have sent them?

Yes. You can use Secure Chat’s message self-destruct capabilities to delete messages you have already sent. We allow you to set a countdown timer on the message which starts both at the moment you hit send, as well as at the moment the recipient opens the message. In both cases, when the timer runs out, the message gets deleted from both devices.

Can I perform factory reset remotely if my device gets stolen or taken away?

Even better – you can perform remote wipe. Deleting files or using factory reset leaves traces of data, which could be enough for people with the right forensic tools to restore your files and data. Our wipe leaves no such traces. It can be triggered remotely via Secure Email or Secure Chat, as well as by us at the user’s request. Secure Phone can also be set to self-wipe if it fails to sync with us a certain number of times (which would happen if it isolated from the outside after being taken away).

What server infrastructure and providers does your service use?

Our service relies only on servers that we own and control. We do not outsource. Our primary data center is located in Sofia, Bulgaria. We have a backup one, at a location we cannot publicly disclose.

How are your servers protected?

Communication between our servers happens through a VPN, and no unencrypted traffic ever leaves our infrastructure or premises. We use logical isolation, firewall filters, ACLs, and DDoS mitigation protection in excess of 1 terabyte of bandwidth. We also have a BGP network to guarantee the constant availability of our services.

How do you respond to government information requests?

Our ability to aid government and law enforcement is technically limited by the fact that we do not store copies of users’ encryption keys, nor messages. Without those, there is no way to decrypt and read the content of any message that goes through our servers.

In the beginning, it took some getting used to dealing with Secure Phone, but quite soon you know exactly how the device works. If you still have questions, however, the service team can even be reached on Sundays and public holidays.

Jan Zevenboom,
Criminal lawyer at Zevenboom Advocatuur.Advocaten