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ty solutions. Accordingly, we actively promotethe use of open and publicly scrutinizedprotocols, mechanisms and algorithms.ConclusionToday, malicious users can easily eavesdropIP traffic, redirect traffic, introduce falsepackets, modify packets, mount denial-ofserviceattacks, and introduce harmful softwareinto systems. One way of counteringthese attacks is to maintain strict control ofaccess to the network by means of firewallsand secure login procedures.To complement access control and obtainthe necessary level of security, the traffic itselfmust be protected. Cryptography providesthe basic techniques needed to buildsecure communications solutions. Protectionmechanisms authenticate users, encryptpackets and protect them from beingmodified.The most straightforward mechanism forregulating access consists of building trustrelationships. Cryptography is used tomaintain the confidentiality of messagesand to guarantee their integrity. Confidentialityis provided by encryption and integritycan be provided by authenticationcodes or digital signatures.Although cryptographic algorithmsmake up the basic mechanisms for securecommunication, standardized methods arebeing sought for authenticating users, ex-changing keys, deciding which algorithmand message formats to use, and so on. Thisis where protocols come into play:• Before a communication session canbegin, the communicating parties mustverify each other's identity. An authenticationprotocol does this. Authenticationcan be based on a public or secret key. Ifpublic keys are used, they are often obtainedusing some kind of public key infrastructure—thisis an essential technologythat can meet the scalability requirementsfor managing keys in networks andfor supporting network services such as e-commerce.• The communicating parties negotiate todetermine which cryptographic algorithmsshould be used for exchanging keysand protecting data.• The parties exchange cryptographic sessionkeys—this phase often includes publickey cryptography, which can be usedto authenticate users and machines and forthe secure exchange of session keys.• Symmetric session keys are calculated andused to encrypt all subsequent packets andto append a MAC field to each packet.Ericsson implements IPsec in many products,including Tigris access servers, Telebitrouters, and GPRS nodes. Ericsson's wirelessLAN solution uses IPsec to encrypt airbornetraffic, and TLS has been used in manyWeb-based applications—in particular, aWAP variant (WTLS) will play an importantrole in the future.REFERENCES1 Menezes, A. J., van Oorschot, P. C. and Vanstone,S. A.: Handbook of Applied Cryptography,CRC Press, 1997.2 Dierks, T. and Allen, C: "The TLS Protocol,"IETF RFC 2246, January 1999.3 Ylonen Et. Al., SSH protocols,http://www.ietf.org/html.charters/secshcharter.html.4 Kent, S. and Atkinson, R.: "Security Architecturefor the Internet Protocol," IETF RFC2401, November 1998.5 Harkins, D. and Carrel, D.: "The Internet KeyExchange (IKE)," IETF RFC 2409, November1998.6 ISO/IEC 9594-8 (1988). CCITT InformationTechnology - Open Systems Interconnection- The Directory: Authentication Framework.Standard X.509,1988.7 Curtin, P. and Whyte, B.: Tigris—A gatewaybetween circuit-switched and IP networks.Ericsson Review Vol 76 (1999):2,pp. 70-81.8 Saussy, G.: The AXI 540 router and the publicIP network edge. Ericsson Review Vol 76(1999):4, pp.182-189.9 Granbohm, H. and Wiklund J.: GPRS—Generalpacket radio service. Ericsson ReviewVol. 76 (1999): 2, pp. 82-88.Ericsson Review No. 2, 2000