D-Link DES-3526 Product Manual - Page 195

xStack® DES-3500 Series Layer 2 Stackable Fast Ethernet Managed Switch User Manual Secure Socket Layer (SSL) Secure Sockets Layer or SSL is a security feature that will provide a secure communication path between a host and client through the use of authentication, digital signatures and encryption. These security functions are implemented through the use of a ciphersuite, which is a security string that determines the exact cryptographic parameters, specific encryption algorithms and key sizes to be used for an authentication session and consists of three levels: 1. Key Exchange: The first part of the cyphersuite string specifies the public key algorithm to be used. This switch utilizes the Rivest Shamir Adleman (RSA) public key algorithm and the Digital Signature Algorithm (DSA), specified here as the DHE DSS Diffie-Hellman (DHE) public key algorithm. This is the first authentication process between client and host as they "exchange keys" in looking for a match and therefore authentication to be accepted to negotiate encryptions on the following level. 2. Encryption: The second part of the ciphersuite that includes the encryption used for encrypting the messages sent between client and host. The Switch supports two types of cryptology algorithms: • Stream Ciphers - There are two types of stream ciphers on the Switch, RC4 with 40-bit keys and RC4 with 128bit keys. These keys are used to encrypt messages and need to be consistent between client and host for optimal use. • CBC Block Ciphers - CBC refers to Cipher Block Chaining, which means that a portion of the previously encrypted block of encrypted text is used in the encryption of the current block. The Switch supports the 3DES EDE encryption code defined by the Data Encryption Standard (DES) to create the encrypted text. 3. Hash Algorithm: This part of the ciphersuite allows the user to choose a message digest function which will determine a Message Authentication Code. This Message Authentication Code will be encrypted with a sent message to provide integrity and prevent against replay attacks. The Switch supports two hash algorithms, MD5 (Message Digest 5) and SHA (Secure Hash Algorithm). These three parameters are uniquely assembled in four choices on the Switch to create a three-layered encryption code for secure communication between the server and the host. The user may implement any one or combination of the ciphersuites available, yet different ciphersuites will affect the security level and the performance of the secured connection. The information included in the ciphersuites is not included with the Switch and requires downloading from a third source in a file form called a certificate. This function of the Switch cannot be executed without the presence and implementation of the certificate file and can be downloaded to the Switch by utilizing a TFTP server. The Switch supports SSLv3 and TLSv1. Other versions of SSL may not be compatible with this Switch and may cause problems upon authentication and transfer of messages from client to host. Download Certificate This window is used to download a certificate file for the SSL function on the Switch from a TFTP server. The certificate file is a data record used for authenticating devices on the network. It contains information on the owner, keys for authentication and digital signatures. Both the server and the client must have consistent certificate files for optimal use of the SSL function. The Switch only supports certificate files with .der file extensions. The Switch is shipped with a certificate pre-loaded though the user may need to download more, depending on user circumstances. To view the following window, click Configuration > Secure Socket Layer (SSL) > Download Certificate: Figure 7- 38. Download Certificate window To download certificates, set the following parameters and click Apply. Parameter Description Certificate Type Enter the type of certificate to be downloaded. This type refers to the server responsible for issuing certificates. This field has been limited to local for this firmware release. Server IP Enter the IP address of the TFTP server where the certificate files are located. Certificate File Name Enter the path and the filename of the certificate file to download. This file must have a .der extension. (Ex. c:/cert.der) Key File Name Enter the path and the filename of the key file to download. This file must have a .der extension (Ex. c:/pkey.der) 180