Transport Layer Security Protocol and Secure Sockets Layer Protocol

The TLS and the SSL protocols use certificates to exchange a session key between the node that initiates the data transfer process (the primary node, or PNODE) and the other node that is part of the communications session (the secondary node, or the SNODE). A certificate is an electronic document that associates a public key with an individual or other entity. It enables you to verify the claim that a given public key belongs to a given entity. Certificates can be self-issued or issued by a certificate authority (see Self-Signed and CA-Signed Certificates for details). When a certificate authority (CA) receives an application for a certificate, the CA validates the applicant's identity, creates a certificate, and then signs the certificate. You use the CA signature to authenticate CA-issued trading partner certificates. A certificate authority issues and revokes CA-issued certificates. Self-signed certificates are created and issued by the owner of the certificate, who must export the certificate in order to create a trusted root for the certificate and supply the trusted root of the self-signed certificate to the partner in a connection.

Levels of Security

The TLS and SSL protocols provide three levels of security:

  • During the first level of authentication called server authentication, the site initiating the session (PNODE) requests a certificate from its trading partner (SNODE), during the initial handshake. The SNODE returns its ID certificate (read from its key certificate file) and the PNODE authenticates it using one or more trusted root certificates stored in a trusted root certificate file (the name and location of which are specified in the remote node record for that specific trading partner in the PNODE's Connect:Direct® Secure Plus parameter file). Root certificates are signed by a trusted source—either a public certificate authority, such as Thawte, or by the trading partner acting as its own CA. If the ID certificate from the SNODE cannot be validated using any root certificate found in the trusted certificate file, or if the root certificate has expired, the PNODE terminates the session. IBM Connect:Direct writes entries to the statistics logs of both nodes, and the session is aborted.
  • The second level of authentication is optional and is called client authentication. If this option is enabled in the SNODE's IBM Connect:Direct Secure Plus parameter file definition for the PNODE, the SNODE will request a certificate from the PNODE, and authenticate it using the information in its trusted root certificate file. If this authentication fails, the SNODE terminates the session and IBM Connect:Direct writes information about the failure to the statistics logs of both nodes.

    In order to perform this security check, the trading partner must have a key certificate file available at its site and the IBM Connect:Direct server must have a trusted root file that validates the identity of either the Certificate Authority (CA) who issued the key certificate or the entity that created the certificate, if it is self-signed.

  • The third authentication level is also optional and consists of validating the PNODE's certificate common name. When the security administrator enables client authentication, they can also specify the common name (CN) contained in the PNODE's ID certificate. During client authentication, the SNODE compares the common name it has specified for the PNODE in its IBM Connect:Direct Secure Plus parameter file with the common name contained in the certificate sent by the PNODE. If the compare fails, that is, the information is not identical, the SNODE terminates the session, and IBM Connect:Direct writes information about the failure to the statistics logs of both nodes.

Areas of Security

The SSL and TLS protocols provide data security in the following areas:

  • Authentication—Certificates used in the SSL or TLS session are digitally signed by a CA through an established procedure to validate an applicant's identity or digitally signed by the certificate owner-issuer. The SSL or TLS protocol validates the digital signature of the certificate being used.
  • Proof of data origin and data integrity validation—The certificate provides proof of origin of electronic transmission and encryption validates data integrity. Message digest (hashing) and encrypting the message digest ensure that the data is not altered.
  • Data confidentiality—Cipher suites encrypt data and ensure that the data remains confidential. The sending node converts sensitive information to an unreadable format (encryption) before it is sent to the receiving node. The receiving node then converts the information back into a readable format (decryption).

TLS Features

Both the SSL protocol and the TLS protocol manage secure communication in a similar way. However, TLS provides a more secure method for managing authentication and exchanging messages, using the following features:

  • While SSL provides keyed message authentication, TLS uses the more secure Key-Hashing for Message Authentication Code (HMAC) to ensure that a record cannot be altered during transmission over an open network such as the Internet.
  • TLS defines the Enhanced Pseudorandom Function (PRF), which uses two hash algorithms to generate key data with the HMAC. Two algorithms increase security by preventing the data from being changed if only one algorithm is compromised. The data remains secure as long as the second algorithm is not compromised.
  • While SSL and TLS both provide a message to each node to authenticate that the exchanged messages were not altered, TLS uses PRF and HMAC values in the message to provide a more secure authentication method.
  • To provide more consistency, the TLS protocol specifies the type of certificate that must be exchanged between nodes.
  • TLS provides more specific alerts about problems with a session and documents when certain alerts are sent.
  • If you are required to have a FIPS 140-2-validated solution, a FIPS-mode of operation is available in Connect:Direct for the TLS protocol.