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UM020107-1211 SSL Configuration

ZTP Network Security SSL Plug-In

User Manual

NullHash_New,

SHA1_New,

NullHash_New

};

Care must be taken while removing the SHA1 digest algorithm. Sometimes this algorithm

is used in the process of signing digital certificates. Therefore, if the SHA1 digest algo-

rithm is not configured into the system and the SSL protocol must either generate or verify

a signature using the SHA1 algorithm, it will not be possible to complete the operation. As

a result, an SSL session will be prevented from becoming established.

It is important to keep the

HashGen array synchronized with the table of cipher suites ref-

erenced by the

pSSL2_CipherSuites, pSSL3_CipherSuites and

pTLS1_CipherSuites pointers. For example, if the SHA1_New function pointer is

replaced with

NullHash_New, then the SHA1 digest algorithm will not be included in the

application. Therefore, if any of the cipher suite tables contains an entry which uses

SHA1, such as

TLS_RSA_WITH_3DES_EDE_CBC_SHA, these cipher suites must be dis-

abled as they will not function properly without the SHA1 algorithm. For more informa-

tion about this topic, see the Cipher Suite Configuration

section on page 31.

Cipher Algorithm Selection

The SSL handshake protocols use symmetric cipher algorithms to encrypt and decrypt

application level data transferred through SSL. With symmetric ciphers, both the client

and server use the same set of keys to encrypt and decrypt data. These symmetric keys are

changed each time the client and server establish a new session. These keys are derived

from information exchanged during the execution of the (asymmetric) PKI algorithm dur-

ing the establishment of a session.

The ZTP Network Security SSL Plug-In recognizes the following four cipher algorithms:

•

RC4 (128-bit key)

•

DES (56-bit key)

•

3DES (168-bit key)

•

AES (128-bit key or 256-bit key) 

Each of these four cipher algorithms has an entry that follows the NullCipher_New func-

tion pointer.

An SSL session is established using any one of these cipher algorithms. However, not all

SSL clients and servers implement the same set of ciphers. By supporting multiple cipher

Note:

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