FAQ
By c.Email Support
By c.Email Support
c.Email at a glance.
FAQs
Overview What is c.Email? c.Email is an app and browser extension that lets you send authenticated, end-to-end encrypted emails from your existing address. Why should I use c.Email? Email, unfortunately, was not designed with security in mind and faces widespread problems with privacy and authenticity. Email providers and hackers can read your emails with impunity, mining them for data to steal or sell to advertisers. Scams and phishing are ubiquitous. To solve this problem, c.Email lets you send authenticated, end-to-end encrypted messages from your existing email address. Email remains ubiquitous because of its simplicity, speed, and availability. We created c.Email from a belief that these features do not have to come at the expense of privacy – and that privacy should be available to everyone. How can I use c.Email? You can download c.Email for iOS on the App Store, or for Android on the Google Play Store. The Chrome extension is available from the Chrome Web Store. How does c.Email work? To use c.Email, just connect your existing email address – you don’t have to create a new account. You then complete a quick, one-time identity check to create your decentralised identity document (DID). This contains your public encryption and verification keys, letting you encrypt and digitally sign your emails. When sending emails, you can then choose between four security levels: Standard: Not authenticated or encrypted. Unencrypted emails can be read by email providers and hackers – leaving you vulnerable to surveillance, data theft, and fraud. Not recommended. Authenticated: Signed with cryptographic proof of the sender’s identity. Secure: Authenticated and protected with post-quantum secure encryption. Can only be read by you and the intended recipient. For when privacy and trust matter. For Your Eyes Only: Authenticated and only decrypted when the intended recipient is looking at the screen. The reader must pass a continuous liveness check using our face unlock technology and a template of the biometric data from their initial identity verification (which is stored on their device, nowhere else). For when absolute secrecy matters. Do I need to create a new account or switch my email? No! c.Email is designed to integrate seamlessly with your existing email accounts, so no need to switch emails or go through a complex setup process. How many email addresses can I add to c.Email? You can add new email addresses to c.Email at any time, with no limit on the number you use. What can I use to prove my identity? You can use a passport or national identity card, as long as it contains a biometric chip. This is because we need to read the data in this chip to store cryptographic proofs of your identity attributes. You can use an expired ID to prove your identity and send authenticated emails in c.Email – however, some future features may require you to have an in-date ID. How do you encrypt my emails? c.Email keeps your emails between you and the people you choose using end-to-end encryption, which means only the sender and recipient of an email can decrypt it. c.Email is not involved in the sending process. Instead, emails are encrypted on your device before sending, remain encrypted in transit, and are only decrypted on the recipient’s device. Nothing is ever stored, encrypted, or decrypted on our servers. This means no-one else can read your emails: not your email provider, and not us, even if we wanted to. The c.Email protocol uses ML-KEM. This is a post-quantum secure system, meaning it is designed to resist attacks even from hypothetically powerful computers in the future. What is the C-layer? The C-layer is our blockchain. For c.Email, it’s where we publish your public encryption key and public verification key. These are public so that you don’t need to exchange them with all your chosen recipients before sending them an email (your decryption key, on the other hand, will always be private and stored only on your device). They are published anonymously – and because they are published on-chain, they cannot be tampered with. What is Cdot? Cdot is our framework for encrypted email, messaging, identity, payments, and recovery. Coming soon, it will be available to users as an app designed for everyday use. There will also be a Cdot SDK for developers to integrate into their own apps, allowing them to build quickly using our privacy-preserving trust stack. If you’re interested in testing or building the next generation of digital privacy products, get in touch. Privacy and security Why do I need to verify my identity just to send emails? We verify your identity to confirm that you are who you say you are and that people can trust your emails. You’ll only have to do this once – afterwards, you can connect new email addresses to c.Email at any time. Why do you need ‘full access’ to my email account? This doesn’t mean we’ll be able to read your emails, send anything on your behalf, or see any other sensitive data. It just means you’ll be able to carry on sending and receiving emails in c.Email – but this time, privately and safely. Why do you need access to my camera? Initially, we need to use your camera to complete the identity check at onboarding. Later on, when you receive a For Your Eyes Only email, you need to be looking at the screen to decrypt it. We use the camera to complete a check against a template of your biometric data, stored on your device. No data is captured or stored at this point. What data do you store, and where? When you carry out your initial identity check, your identity information and a template of your biometric data is stored on your device only – they never go anywhere else. This is so you can use our For Your Eyes Only setting (which ensures emails are only decrypted when the intended recipient is looking at the screen, preventing your emails from being read even if your device is stolen when unlocked). Once you have confirmed your identity, we turn your email address into a hash-based message authentication code (HMAC). This is a hash of your email address, combined with a secret key, then hashed again. We link the HMAC to your public verification key and public encryption key via a smart contract executed on our blockchain (the C-layer). The purpose of this is to rule out brute-force guessing of email addresses. When you send or receive an email, c.Email corresponds with the C-layer to retrieve the relevant public key to encrypt and/or authenticate it. These keys are indexed by an arbitrarily chosen random identifier. Our server maintains a mapping from email HMACs to these random identifiers. We don’t store, encrypt, or decrypt any of your data on our server. When you read a For Your Eyes Only email, the content is only decrypted if you continuously pass a liveness check. No data is captured or stored from this check. Your private decryption key, as well as your identity data, remain on your device at all times, and nowhere else. For more information, you can read our privacy policy. A hash is a cryptographic function that converts any piece of data into a fixed-length string of numbers and letters. It is one-way, not reversible: meaning the original data cannot be discovered from the hash. This is why it is safe to store on a blockchain. Why should I trust you with my biometric data? You don’t need to, because we don’t have it in the first place. c.Email doesn’t store your information anywhere but your device, which means it’s not accessible to anyone else – not even us. The reason we ask for it is because it provides greater security than relying on passwords. We will never share your personal data, ever. If you care so much about privacy, why do I need every email to display my full real name? Certonymity is committed to building an internet where privacy is a core feature, not a complicated add-on. Email, by definition, can never be fully anonymous – it’s just not what it’s for. But it’s a key part of the internet (and in many cases, a key part of life full stop) – so we think everyone should able to send private, safe emails. Our email authentication feature allows people to send and receive emails without fear of fraud, impersonation, or phishing attacks. Anonymous messaging can be saved for other platforms. Has c.Email been audited for security? C.Email’s data handling and security has been validated by the Cloud App Security Assessment framework, developed by the App Defense Alliance. This verifies that we can securely handle user data and delete it upon request. Users can delete their data at any time by uninstalling the app or emailing delete-account@certonymity.com. Using c.Email How do I sync the c.Email app with the Chrome extension? Once you’ve installed the Chrome extension, you first need to set up a passkey. This encrypts the database containing your private keys for encrypting and authenticating emails, which remains on your browser and nowhere else. The extension will prompt you to do this. After creating your passkey, you’re ready to sync your private keys. To do this: 1. Open c.Email on your phone (the QR code won’t work with your camera app). 2. Tap Account details. 3. Tap Link device. 4. Scan the QR code. You can now start using c.Email in your browser. Only you can sync your keys – if someone else tried to scan your QR code, they’d have to prove ownership of your email address. All information exchanged between your browser and the c.Email app is encrypted. We don’t have access to this data or the key to decrypt it. Can I search my emails even if they’re encrypted? Yes. Emails stored locally (i.e. any email you’ve received or searched for since installing c.Email) can be searched, because emails are decrypted on your device rather than on our servers. Emails not stored on your device (i.e. historical emails pre-dating your use of c.Email) are still searchable, but only with the text in their sender addresses and subject lines. For this reason, these elements are not encrypted in c.Email. If you type your search query and don’t immediately see the email you’re looking for, hit the search button. This triggers a query to the API, which returns all relevant results rather than just the emails stored on your device. Can I send encrypted emails to anyone? You can send an encrypted email to any address, but to read the decrypted text, the recipient will need to be on c.Email. If I send a non-encrypted email, will it still show my verified identity? No. Unencrypted (or ‘not secure’) emails will display the message ‘Real name: unverified’ below your name, even if you have verified your identity before sending. This is because emails can only be sent authenticated and encrypted, or not authenticated or encrypted. Why are some emails highlighted in red? On very rare occasions, you may also see emails highlighted in red and marked ‘dangerous’. This means an email signature is invalid and the sender’s identity cannot be verified. In the majority of cases, this is because a verification key has gone missing for some reason, which means the email has been sent encrypted but cannot be authenticated. (Theoretically, a ‘dangerous’ email could also indicate that someone is trying to impersonate our app.) For example, you could see emails marked as ‘dangerous’ if you have re-verified your identity since receiving the email, but haven’t been through our account recovery process. You won’t be able to read or reply to emails marked in red. Can I recover my account if I lose access? Yes. Your private key for email decryption is stored on your device to avoid compromising your privacy. However, to prevent you losing your email data if you lose access to your device, c.Email automatically encrypts a backup key for you. The retrieval process for this key is only triggered when you sign in using biometrics on a new device. When you first download c.Email, you will be prompted to set a password for your backup. Once you have done this, c.Email automatically encrypts and uploads a backup key to your cloud provider, such as Google Drive, iCloud, or OneDrive. To recover your data, install c.Email on a new device and choose the email address you were using previously. Once you have completed authentication with your email provider and identity verification with c.Email, you will be asked for your backup password. c.Email will then retrieve the encrypted backup from the cloud and restore your keys. You can configure this process and change your backup password in your c.Email settings. Is c.Email available for businesses? Yes – we have two implementation options available. Level 1 is our self-serve encryption service, with emails encrypted and decrypted on either your existing mail server or a new secure server provided by us. Level 2 offers highly secure client-side encryption, with one decentralised identity document (DID) per business. See c.Email for businesses for more. How does setup work with c.Email for businesses? We have two implementation options available. Level 1 is our self-serve encryption service, with emails encrypted and decrypted on either your existing mail server or a new secure server provided by us. Level 2 offers highly secure client-side encryption, with one decentralised identity document (DID) per business. See How it works above, or contact us for more information. How can I contact the c.Email team? For all support queries, please email support@certonymity.com. For other enquiries, please email info@certonymity.com.
Contact
For press enquiries, please email press@certonymity.com or view our press kit here. For customer support or questions about using c.Email, please go to our help centre or email support@certonymity.com. For any other enquiries, please email info@certonymity.com.