STARTTLS is a command that is used to upgrade an existing plaintext connection to a secure, encrypted (TLS) connection. It is used with protocols such as SMTP (Simple Mail Transfer Protocol), which do not natively support encryption.
When a client wants to establish a secure connection with a server using STARTTLS, it sends a STARTTLS command to the server. If the server supports STARTTLS, it will respond with a message indicating that it is willing to upgrade the connection to a secure, encrypted TLS connection. The client will then initiate the TLS handshake process to establish the encrypted connection.
To use STARTTLS, you will need to follow these steps:
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Establish a plaintext connection with the server. This can be done using a protocol such as SMTP (Simple Mail Transfer Protocol) or IMAP (Internet Message Access Protocol).
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Send a STARTTLS command to the server. The exact syntax of the STARTTLS command will depend on the protocol you are using. For example, in SMTP, you would send the following command:
STARTTLS. -
If the server supports STARTTLS, it will respond with a message indicating that it will upgrade the connection to a secure, encrypted TLS connection.
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Initiate the TLS handshake process to establish the encrypted connection. This involves exchanging certificates and keys to establish the encrypted link.
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Once the TLS connection has been established, all communication between the client and server will be encrypted and protected from tampering and interception.