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Using Ciphers for Inbound SSL Connections

This topic describes the use of ciphers for inbound SSL (HTTPS and FTPS) connections with the Server. For the procedure for configuring SSL on EFT, refer to Enabling SSL on the Server.

EFT validates inbound SSL sessions, and allows or denies connections based on ciphers specified on the Server's Security tab. During SSL negotiation, the connecting (inbound) SSL client is allowed to select its preferred combination from the specified list.

  • The PCI DSS states that you should use strong ciphers and protocol versions. On a high security-enabled Site, if you attempt to specify weak ciphers and protocol versions or to create a cipher manually, the Server prompts you to correct it, or continue with reason.

  • If FIPS mode is enabled for SSL connections, only FIPS-approved SSL ciphers are available (AES 256 bit, 3DES 168 bit, AES 128 bit).

EFT provides two options for specifying ciphers:

  • Select algorithms and order by preference—(selected by default) If this list is used to specify more than one approved cipher, and the connecting client has in its list one or more ciphers that are also on EFT’s approved list, EFT selects and uses the cipher based on ordering (priority) shown in the list box. You can change the priority by clicking the up and down arrows to the right of list. Click Reset to Defaults to clear any edits. You can choose one or more ciphers available from the OpenSSL library installed with EFT. At least one check box must be selected.

  • Manually specify algorithms—This selection uses the parameterized cipher string for creating an ordered SSL cipher preference list per https://www.openssl.org/docs/man1.0.1/apps/ciphers.html. The cipher negotiation will use the ordering defined by the user in the cipher string (for example @STRENGTH) or, if no ordering was defined, the default ordering.

    • When Manual is selected, the Select list is disabled, and the advanced ciphers string list is used. Provide a string that will be passed directly to the SSL library.

    For example:

    ALL:!ADH:RC4+RSA:+SSLv2:@STRENGTH

    or

    ALL:!ADH:HIGH:@STRENGTH

    Each cipher is separated by a colon and can be preceded by the characters !, -, or +.

    • ! (exclamation point) = the ciphers that follow are not to be used

    • + (plus sign) = the ciphers are moved to the end of the list

    • If none of these characters is used, then the string is interpreted as a list of ciphers to be used.

    • @STRENGTH can be used at any point to sort the current cipher list in order of encryption algorithm key length.

    • To exclude 0-bit ciphers, do not use COMPLEMENTOFALL; use !NULL

    • Use ALL:!EXPORT:!LOW to exclude 40- and 56-bit ciphers, as shown in the table below.

    • Use ALL:COMPLEMENTOFALL to allow all off the supported ciphers, as shown in the table below.

    Refer to The OpenSSL ciphers page for details of cipher strings, including examples.

    EFT validates the cipher string against the SSL library once when Apply is clicked or if the user clicks away from the Security tab. If the string is faulty, EFT returns an error indicating that it failed and the failure reason, if available. After the prompt appears and you click OK or Cancel, the prompt closes, but does not clear out the cipher box in case you want to refine it, if needed. Changes cannot be applied until the string is valid. (Or you can go back to the Select list, then click Apply.)

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