Mailfence security analysis

Mailfence is a secure and private email service that provides end-to-end encryption email and digital signing features. All crypto operations relating to the private keys, and the bodies of emails are performed after the user unlocks the private key with the respective passphrase that only the user knows.

The following table will provide a high-level security analysis overview of Mailfence with respect to the type of information and the level of protection that it holds.

Type of Information

Level of Protection

Source of random data when creating new PGP keys Entropy collected via the client device
Password encrypted in transmission from browser to web server SSL/TLS
Password securely stored on the web server SHA256 (iterated and hashed)
Private key passphrase exposure Passphrase check for all crypto-activity always occurs on the client side – and never gets exposed to the server
Encrypted private key in transmission between browser and web server Two layers of encryption:
1- With user passphrase (via AES)
Encrypted private key in storage With user passphrase (via AES)
Private key decrypted on the web server This does not apply to Mailfence – as all the private key en(de)cryption occurs on the client side with the user passphrase
End-to-end encrypted messages during transmission from the client browser to Mailfence servers Two layers of encryption:
1 – OpenPGP
End-to-end encrypted messages body and attachments during transmission between web server and recipient email account 1 – OpenPGP
2 – STARTTLS (if supported by the recipient)
End-to-end encrypted messages body & attachments encrypted in the storage on the web server OpenPGP
End-to-end encrypted messages body & attachments known to the web server No (except sent & draft items) – crypto-operations concerning end-to-end occur on the client side
Message headers are encrypted during transmission from the browser to the web server SSL/TLS
Message headers are encrypted during transmission between the web server and the recipient email account STARTTLS (if supported by the recipient)
Message headers in storage on the web server Not encrypted

Vulnerability Analysis

The following points apply to emails sent using end-to-end encryption:

Attack Level of Protection
Attacker is listening to your Internet connection Protected
Attacker gets access to email stored on the server Protected
Attacker gets access to the server’s databases Protected
Attacker compromises the webserver after you have accessed your email Protected
High-level MiTM attack – where an adversary sends you a false code for all the crypto-related operations to check Not Protected
Attacker has access to your account Protected (but the sent end-to-end encrypted messages will be viewable in clear text)
Attacker has access to your computer before you access your email (and can install programs such as key logger/malware…) Not Protected

Don’t hesitate to contact us in case you have more questions about Mailfence’s security analysis.

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