Internet security
Foreword
The 90th generation is due to the opening and commercialization of Internet to develop. But openness has brought system invasion and other security issues. Based on TCP / IP protocols and Intranet, which uses Internet-based communication standards and web information circulation modes, therefore people need a more secure Internet. There are currently two security services: First, access control, prohibiting illegal communication and networking; second, communication security services, providing the integrity, reliability of authorization data, and access to accessions to the same level.
When the user connects to the Internet, the control association of one or several intermediaries can be inserted in the middle to prevent attacks through the network, and provide a single security and auditing installation control point, which is a firewall. The firewall includes two types of packet filtering routers (SR) and proxy servers.
SR is a multi-port IP router; the proxy server is a representative of the user's user, which is actually a gateway on an application layer. When the user uses TCP / IP applications, provide legal identity and authorization information to Proxy, proxy is connected to the host, and relays the IP packet between two communication points. The process of IP packet processing is transparent to the user.
The advantage of SR is simple, low cost; the disadvantage is that it is difficult to accurately set pack filters, lack user-level licenses, and router suppliers are committed to solving this problem and propose standardized user-level authorization agreement RADIUS. The advantage of Proxy is that there is a user-level authorization; the disadvantage is that all applications must establish an application layer condition, which will seriously affect the deployment of the new application.
SR is usually mixed with the proxy service fireproofer, which mainly prevents attacks on IP. The most extensive deployment of the firewall is a double hole guardian gateway, a screen of the host gateway, and a screen gateway, a screen gateway, and a screen gateway firewall, and a SCREENED SUBNET. The firewall advocate believes that the firewall sets various safety functions to simplify installation and management; some of the problems and inconveniences bringing multiple registrations, external mechanisms, and their interaction between the alarm wall, and It is more and more obvious to attack from the internal attack. Although internal firewalls can continue to be set in intranet, there are still many problems and vulnerabilities that cannot be resolved. In addition, the firewall cannot block the input of data (malicious), such as viruses. With the widespread use of Java, Java Script, this issue will become more and more serious. Another disadvantage of the firewall is that the vendor rarely provides a key solution solution.
Internet layer security
In the past 10 years, in order to develop standardized network or Internet security protocols, several programs have proposed several programs, such as the SP3 network layer security protocol proposed by NSA and NIST, ISO proposed NLSP, which can be IP and CLNP Service NIST Protocol I NLSP, Ioannidis and Blaze, another Internet layer security protocol Swipe, etc. All of these agreements are more than different, and IP is incorporated into enabling technology. It is encrypted and encapsulated in Out IP header in Out IP Header, and the package is decrypted and sent in the outline system. destination.
The Internet Engineering Task force establishes the Internet Security Protocol Working Group is responsible for IPSP (IP Security Protocol) and IKMP (Internet Key Management Protocol). The mechanism established by IPSP applies to current IP version IPv4 and new version IPv6, and independent algorithm. The working group proposed AH (Authentication Header) and ESP (Endapsulating Security PayLoad): AH provides source authentication and integrity assurance; ESP provides reliability. IP AH is a message code calculated before the IP package transmits, and the sender uses the Cryptography Key calculation AH, the recipient uses the same or another key to verify. The main idea of IP ESP is to package the entire IP package (tunnel mode) or only the data (transmission mode) of the ESP high-level protocol, and add a new IP header to most ESP encrypted tunnels, mode encrypted ESPs. To determine the path on the Internet. The receiving end removes the IP header and options of the text, and the IP package can be handled after the ESP is decrypted. RFC1827 defines the form of ESP, and RFC 1829 defines data encryption standards, which is encrypted and decrypted in the CPC (Cipher Block Chaining). The AH and ESP mechanisms can be used separately or mix, but both of them cannot provide flow analysis.
In August 1995, IESG approved IPSP's RFC as an Internet tracking standard, with SHA (Secure Hash Algorithm) instead of MD5, with Triple DFS instead of DES. The IP SEC Working Group made standardization work on standard code management protocols and made some reference:
IBM's MKMP;
Sun Microsystem's SKIP;
Phil Karn's The PhiMAGEMENT Protocol;
Hugo Krawcyk's SKEME; NSA's IsakMP;
Hilarie Orman's The Oakley Key Determination Protcol.
These protocols are basically the same, but there are some differences: In addition to MKMP, they all need a full-operated public code, but MKMP assumes that both ends share a manual distribution; except Skip requires Diffie Hellman authentication, the rest of the protocol Require RSA certification. In September 1996, Oakley in the IsakMP framework was managed as a mandatory code of IP SEC.
The main idea of the PhoTuris and the PhoMis Like protocol is to convert each new dialogue system with a Diffie Hellman code to turn the signature subsequence into a Diffie Hellman parameter to prevent anyone from attacking in the middle. If intruders decline a long-term private password such as PhSA code or SKIP's Diffie Hellman code, the invader can only disguise into an entity that has a code, but does not decode the message in the past or future.
Skip does not provide BTP and PFS, but use Diffie Hellman Key Exchange, which is not accurate, ie, two dooms know that the eccentric Diffie Hellman public code does not accurately share a master code, and A code derived from the package (including the IP package) encrypted. Each IP package may decrypt and encrypt in different code, SKIP is required to provide BTP and PFS similar to the PhiTURIS and the PhiTuris Like protocol, the difference is that SKIP requires Diffie Hellman test. Any security protocol for INTERNET today is easy to implement and deploy. But the problem is that most IPSP implementations and key management protocols are based on UNIX SYSTEM source, while MS DOS and Windows systems are unacceptable. To solve this problem, Wanger and Bellovin have established a complete IP sec mode under IP.
The main advantage of Internet layer security is transparency; the main disadvantage is a software package that is unclear process, as it uses the same access policy-encryption key for all packages sent to the same address, so RFC1825 allows users to users The key application is slightly improved, but the user's key application requires the operating system core to make great adjustments.
Transport layer security INTERNET
Applications typically deal with different levels of security protocols using IPC (Interporcess Communications Facility) in different transport layer protocols. The most popular IPC interface is BSDSockets and TLI. You can find it in the UNIX system V command. The first idea of providing secure services in the Internet is to strengthen its IPC interface, such as BSD sockets, etc., the specific practices include the authentication of the dual-end entity, the exchange of data encryption keys, etc. Netscape Communications Follow this idea to develop a security cache protocol based on a reliable transmission service (such as TCP / IP) (SSL: Secure Sockets Layer) can now provide the most reliable transmission service. SSL V3 issued in November 1995 has the following main agreements:
SSL recording protocol, which involves segmentation, compression, data authentication, and encryption of information provided by the application. The SSL V3 provides support for the MD5 and SHA and SHA and data encrypted by data authentication, which can be negotiated with the data to authenticate and encrypt data can be negotiated through the SSL's handshake protocol. Processing debris, compressed data, data confirmation, encryption for application; RC4 is encrypted on DEC's data;
SSL handshake protocol is used to exchange version numbers, encryption algorithms, (mutual) authentication and switch key. SSL V3 provides support for the Defie-Hellman key exchange algorithm, RSA-based key exchange mechanism and another key exchange mechanism that implements on Fortezza CHIP.
The SSL Handshake protocol handles the conversion of different version protocols, supports the Ceyptography algorithm. SLL V3 supports KEY Exchange, Diffie Hellman and RSA.
Netscape Communications has launched an SSL reference implementation (called SSLREF) to the public. Another free SSL implementation is called SSLEAY. SSLREF and SSLEAY provide any TCP / IP application to provide SSL features. The Internet Number Assignment Authority (IANA) has allocated a fixed port number for an application with SSL function, for example, the port number of HTTP (HTTPS) assigned by SSL is 443, and the port number assigned by SSL SMTP (SSMTP) is 465. The port number assigned by the NNTP (SNNTP) with SSL is 563.
Microsoft launched an improved version of SSL2 called PCT (private communication technology). At least from the record format it uses, SSL and PCT are very similar. Their main differences are different on the most significant position of the version number field: SSL This bit takes 0, and the PCT is taken 1. After this, you can support these two protocols. In April 1996, IETF authorized a transport layer security (TLS: Transport Layer Security) Working Group to develop a transport layer security protocol (TLSP) so as to be officially submitted to IESG as a standard proposal. TLSP will look like SSL in many places. The main advantage of the Internet layer security mechanism, which has been described above is that its transparency, that is, the security service provides no change in the application layer. This is not available for the transport layer. In principle, any TCP / IP application, as long as the transport layer security protocol, such as SSL or PCT, you must perform several modifications to increase the corresponding function, use (slightly) different IPC interface, main reason is the transmission layer security The service is based on Process to Process, instead of Host to Host. This issue can be further improved by applying layer security services. Thus, the main disadvantage of the transport layer safety mechanism is to modify the transmission layer IPC interface and the application. However, the modification here is quite small compared to the security mechanism of the Internet layer and the application layer. Another disadvantage is that UDP-based communications is difficult to establish a security mechanism in the transport layer. Compared with the network layer security mechanism, the main advantage of the transport layer security mechanism is that it provides process-based processes (rather than hosts) security services. This achievement can be quickly spanned forward if the application level security service is counted.
Applicable layer
Must keep in mind (and carefully taste): The security protocol of the network layer (transport layer) allows for security properties to increase the data channel between the host (process). Essentially, this means that true (perhaps plus confidential) data channel is also built between the host (or process), but it is impossible to distinguish a security requirement of a specific file transmitted on the same channel. For example, if a host is established between another host, a secure IP channel is established, then all IP packets transmitted on this channel are automatically encrypted. Similarly, if a process and another process establishes a secure data channel through the transport layer security protocol, all messages transmitted between the two processes are automatically encrypted.
If you really want to distinguish a different security requirement of a specific file, you must use the security of the application layer. Providing application layer security services is actually the most flexible means of processing a single file security. For example, an email system may need to implement data signatures of individual paragraphs to be issued. The safety function provided by the lower layer protocol generally does not know any of the paragraph structure of the letter to be issued, so that it is impossible to know which part of the segment is signed. Only the application layer is the only level that can provide this security service.
In general, there are several possible practices that provide security services in the application layer, the first thing that is ideal is probably modified separately for each application (and application protocol). Some important TCP / IP applications have been doing this. In RFCs 1421 to 1424, IETF specifies private reinforcing mail (PEM: Privacy Enhanced Mail) to provide security services based on SMTP-based email systems. Due to various reasons, the Internet industry adopts PEM's step or slow, a primary reason is that PEM relies on a existing, fully operable PKI (public key infrastructure). PEM PKI is a hierarchical, consisting of three levels:
The highest layer: Internet security policy registration body (ANTERNET Policy Registration Authority).
Intermediate layer: Policy Certification Authoritiy.
Layer 3: Certification Authoritiy.
Building a PKI that conforms to PEM specifications is also a political process because it requires multi-party to reach trust in common. Unfortunately, history shows that political process always takes time, as an intermediate step, Phil Zimmermann has developed a package called PGP (PRETTY Good Privacy). PGP is in line with the vast majority of PEM, but does not have to ask PKI's presence. Instead, it uses a distributed trust model that determines which other users of trust by each user. Therefore, PGP is not to promote a global PKI, but let users build their own trust. This immediately produces a problem, which is to abolish it under the distributed trust model. S-HTTP is a security enhancement version of Hypertext Transfer Protocol (HTTP) used on the Web, designed by corporate integration technology. S-HTTP provides a file-level security mechanism, so each file can be set to a private / signature. Algorithms used as encryption and signatures can be negotiated by both parties involved in communications. S-HTTP provides support for a variety of one-way hashing (HASH) functions, such as: MD2, MD5 and SHA; support for multiple single key systems, such as: des, ternary DES, RC2, RC4, and CDMF For support for digital signature institutions, such as RSA and DSS.
There is currently no recognition standard for web security. Such standards can only be developed by WWW consortium, IETF, or other relevant standardized organizations. The official standardization process is long, it may be dragged in several years until all standardized organizations fully recognize the importance of Web security. S-HTTP and SSL provide Web security from different angles. S-HTTP is distinguished by a single file, while SSL is supervised by "private" and "certified" in the data channels involved in communication. Terisa's SecureWeb Tools package can be used to provide security features for any web application. The tool package provides an encrypted algorithm with RSA Data Security and provides comprehensive support for SSL and S-HTTP.
Another important application is e-commerce, especially credit card transactions. In order to make the credit card transaction security on the Internet, Mastercard has developed a secure electronic payment agreement (SEPP), VISA International and Microsoft (and other companies in the same way). (STT) protocol. At the same time, MasterCard, Visa International and Microsoft have agreed to join hands to launch a secure credit card trading service on the Internet. They released the appropriate security electronic transaction (SET) protocol, which specifies the method of paying the credit cardholder with its credit card through the Internet. The background of this mechanism has an infrastructure issued by a certificate to provide support for the X.509 certificate.
All of these plus security functions mentioned above face a major problem, that is, each such applications are individually modified. Therefore, if there is a unified modification, it is much better. One step to this direction is the safety shell (SSH) developed by the University of Helsinki University. SSH allows its users to securely log in to the remote host, execute commands, and transfer files. It implements a key exchange protocol, as well as the host and client authentication protocol. SSH has free versions on the popular multi-Unix system platform today, as well as commercialized versions of Data Fellows.
Push the SSH's idea to first, and go to the authentication and key distribution system. Essentially, the authentication and key distribution system provides an Application Programming Interface (API) that can be used to provide security services for any network application, such as authentication, data confidentiality, and integrity, access control, and non-denial services. . There is already a practical authentication and key allocation system, such as: MIT's Kerberos (V4 and V5), IBM Cryptoknight and NetWrok Security Program, DEC's SPX, Karlsruhe University's Index Safety System (TESS), etc. Examples widely used. You can even see the modifications and expansion of some authentication and key allocation systems. For example, SESAME and OSF DCE have added an increase in access control services to Kerberos V5, and Yaksha has added an increase in non-denial of service for Kerberos V5. One of the frequent encountered issues about the authentication and key allocation system is about the cold encountered on the Internet. One reason is that it still requires a change to the application itself. Considering this, a standardized security API provides a standardized security API for an authentication and key distribution system. At this point, developers don't have to increase the overall application of the entire application for the addition of few safety features. Therefore, one of the most important progress in the field of certification system design is to develop standardized security APIs, which is a general security service API (GSS-API). GSS-API (V1 and V2) may still be too technored by programmers of a non-security expert, but the safety network programming (SNP) developed by researchers in Texas Austin University, which makes the interface than GSS -API higher levels make the programming related to network security more convenient.
