Encrypted client/server communication

Data classification

It depends on the nature of the data but in general “sensitive” information could be: user logins, passwords, user details (such as names, addresses, contact details, etc.), email addresses and other data which are not public. Medical, financial data (e.g. credit card details, account numbers, access codes, etc.) and others, are confidential by their nature and must not be transmitted unencrypted at all.

In most cases, a data assessment should be undertaken to classify the data according to several traits relating to use, legal requirements, and value. The outcome of this assessment can be a categorization based on a data classification model, which then defines how to protect the data.

Public Public Restricted Organization Confidential Organization Secret
Type non-sensitive externally sensitive internally sensitive extremely sensitive
Disclosure impact none limited significant sever
Access restrictions none low (e.g. username/ password) high (e.g. public/private key + geolocation) very high
Data transport unencrypted unencrypted but protected encrypted highly encrypted
Storage requirements none unencrypted but protected encrypted highly encrypted

The secure and maybe encrypted storage of sensitive data should also be considered.

The most secure first paradigm in most cases is: do neither transmit nor store any sensitive data if not absolutely required.


Secure Sockets Layer (SSL) is an industry standard and the current security technology for establishing an encrypted link between a browser (client) and a web server. This protocol provides encrypted, authenticated communications across the Internet and ensures that all data passed between client and server remains private and integral. It is based on a public/private key technology and uses certificates which typically contain the domain name and details about the website operator (e.g. company name, address, geographical location, etc.). Recent discussions are questioning the organizational concept behind SSL certificates and the “chain of trust”, but the fact is that SSL is the de facto standard today and still is considered secure from a technical perspective.

Whenever sensitive data is transferred between a client (the visitor of the website) and the server (TYPO3 website), a SSL encrypted connection should be used.

When using payment gateways to process payments for online shops for example, most financial institutions (e.g. credit card vendors) require appropriate security actions. Check the policies of the gateway operator and card issuers before you institute online payment solutions.


A risk of unencrypted client/server communication is that an attacker could eavesdrop the data transmission and “sniff” sensitive information such as access details. Unauthorized access to the TYPO3 backend, especially with an administrator user account, has a significant impact on the security of your website. It is clear that the use of SSL for the backend of TYPO3 improves the security.

TYPO3 CMS supports a SSL encrypted backend and offers some specific configuration options for this purpose, see configuration option “lockSSL” in chapter “Guidelines for TYPO3 integrators”.

However, the access details used for the login are transferred between the client and the server when submitting the login form only. After a successful login, a session ensures that the user remains authenticated. This results in the conclusion, that only the login procedure should be protected, not the following client/server communication necessarily – assuming no sensitive information are accessed from or stored in the backend.

The TYPO3 CMS core extension “rsaauth” addresses this requirement, see “security-related core extensions” in chapter “Guidelines for TYPO3 integrators”.

Other services

An encrypted communication between client and server for other services than the TYPO3 frontend and backend should be considered, too. For example, it is highly recommended to use encrypted services such as SSH (secure shell), SFTP (SSH file transfer protocol) or FTPS (FTP-Secure) instead of FTP, where data is transferred unencrypted.