1-Factor vs. 2-Factor Authentication

1-Factor authentication simply refers to a memorized password, which can be copied with relative ease. 2-Factor authentication is the memorized password of an external token used in conjunction with the physical token. Access can only be granted when the two are used together.

Thus, 2-factor authentication is something you know, used together with something you physically have.

 

Access Control

The process of preventing unauthorized access to the resources of an IT product, programs, processes, systems, or other IT products. Some suppliers consider preventing unauthorized users from logging on to the system to be access control. In reality, access control should also s logged-on users accessing objects (files, devices, etc) for which they have no authorization.

 

Access Control List

An access control list (ACL) is a table that tells a computer?s operating system which access rights each user has to a particular system object, such as a file directory or individual file. Each object has a security attribute that identifies its access control list. The list has an entry for each system user with access privileges. The most common privileges include the ability to read a file (or all the files in a directory), to write to the file or files, and to execute the file (if it is an executable file, or program). The list is implemented differently by each operating system.

 

AES

The ?Advanced Encryption Standard?, which will replace DES (Data Encryption System) in the near future.
 

Alice

The name traditionally used for the first user of cryptography in a system; Bob's friend.

 

Algorithm

A mathematical procedure that can manipulate data. Cryptographic algorithms are used to encrypt sensitive data files, to encrypt and decrypt messages, and to digitally sign documents.

 

APDU

The APDU (Application Protocol Data Unit) is a set of native commands that enable software to communicate with the eToken directly, rather than through a higher level API like CAPI or PKCS#11.
 

Asymmetric Cryptography

See Public Key Cryptography

 

Authentication

Authentication is the action of verifying information such as identity, ownership or authorization. In private and public computer networks (including the Internet), authentication is commonly done through the use of logon passwords. Knowledge of the password is assumed to guarantee that the user is authentic. Each user registers initially (or is registered by someone else), using an assigned or self-declared password. On each subsequent use, the user must know and use the previously declared password. The weakness in this system for transactions that are significant (such as the exchange of money) is that passwords can often be stolen, accidentally revealed, or forgotten.

For this reason, Internet business and many other transactions require a more stringent authentication process. The use of digital certificates issued and verified by a Certificate Authority (CA) as part of a Public Key Infrastructure (PKI) is considered likely to become the standard way to perform authentication on the Internet. Logically, authentication precedes authorization (although they may often seem to be combined).
 

Block Cipher

A symmetric cipher, which encrypts a message by breaking, it down into blocks and encrypting each block.
 

Bob

The name traditionally used for the second user of cryptography in a system; Alice's friend.

 

Brute Force Attack

This attack requires trying all (or a large fraction of all) possible values till the right value is found; also called an exhaustive search.
 

CA (Certification Authority)

A certification authority is a trusted third party who confirms the identity of an organization. The CA will first satisfy itself that an organization is exactly who or what it claims to be, and will then issue that organization with a 'certificate'. The certificate is likely to be in the form of an electronic key or value. A trading partner can present it electronically to the CA for verification and confirmation at any time.
In some ways the certificate is analogous to a credit card. Both the certificate and the credit card allow two parties to trade with some degree of security without any further proof of identity.

 

Certificate

In cryptography, an electronic document binding some pieces of information together, such as a user's identity and public-key. Certifying Authorities (CA's) provide certificates.
 

Certificate Revocation List (CRL)

A list of certificates that have been revoked before their expiration date.

 

CertStore

In Windows, public-key objects such as certificates, CRLs (Certificate Revocation Lists), and CTLs (Certificate Trust Lists) are stored in certificate stores for use by users, services, and computers. The Windows certificate stores include physical stores and logical stores.

The physical certificate stores are where public-key objects such as certificates, CRLs, and CTLs are physically stored either locally in the system registry of the computer, or on an eToken, or remotely in Active Directory. Many of the public-key objects in the physical stores are shared among users, services, and computers through the use of logical certificate stores.

Logical certificate stores group certificates together in logical, functional categories for users, computers, and services. Logical certificate stores contain pointers to the physical certificate stores. Changes to the logical certificate stores are made to the appropriate physical stores that are located in the system registry or on an eToken or in Active Directory. Because you use only the logical certificate store for a user, service, or computer, you neither have to keep track of where the certificates are actually stored, nor do you have to edit the system registry to manage the certificate stores.

 

CHAP

Challenge Handshake Authentication Protocol. Security feature supported on lines using PPP encapsulation that prevents unauthorized access. CHAP does not itself prevent unauthorized access, it merely identifies the remote end. The router or access server then determines whether that user is allowed access. Compare to PAP.

 

Ciphertext

Data that has been scrambled by encryption.

 

Computer Fraud

The deliberate misrepresentation, or unauthorized disclosure or alteration of data; usually for personal and monetary gain.
 

CryptoAPI (CAPI)

Microsoft® Cryptographic Application Programming Interface (CryptoAPI or CAPI) provides services that enable application developers to add security based on cryptography to applications. CryptoAPI includes functionality for encoding to and decoding from ASN.1, hashing, encrypting and decrypting data, for authentication using digital certificates, and for managing certificates in certificate stores. Encryption and decryption are provided both using session keys and with public/private key pairs.
 

Cryptology

The study of techniques that can be used to conceal information, or reveal information that has been previously concealed; that is, the combination of cryptanalysis, cryptography and steganography.
 

Decryption

The process of unscrambling ciphertext and returning it to plaintext



 

Default Password

A password contained in a system when first delivered and installed. If you accept delivery of any product containing a default password, hardware or software, you should change the password as soon as possible.


 

DES Encryption

Data Encryption Standard (DES) is a widely used method of data encryption using a private (secret) key that was judged so difficult to break by the U.S. government that it was restricted for exportation to other countries. There are 72,000,000,000,000,000 (72 quadrillion) or more possible encryption keys that can be used. For each given message, the key is chosen at random from among this enormous number of keys. Like other private key cryptographic methods, both the sender and the receiver must know and use the same private key.



 

DESX 128-bit Encryption

DESX (DES eXtended) is an encryption algorithm that extends the famous DES (Data Encryption Standard) algorithm to a key size of 128 bits, by adding two complex operations that further strengthen its efficiency and security. Deciphering a message encrypted with DESX requires finding the right random information out of a total of 2118 operations, which has been mathematically proven to be impractical.


 

Digest

Commonly used to refer to the output of a hash function, e.g. message digest refers to the hash of a message.


 

Digital Signature

A digital signature is an electronic rather than a written signature that can be used by someone to authenticate the identity of the sender of a message or of the signer of a document. It can also be used to ensure that the original content of the message or document that has been conveyed is unchanged. Additional benefits to the use of a digital signature are that it is easily transportable, cannot be easily repudiated, cannot be imitated by someone else, and can be automatically time-stamped.

A digital signature can be used with any kind of message, whether it is encrypted or not, simply so that the receiver can be sure of the sender's identity and that the message arrived intact. A digital certificate contains the digital signature of the certificate-issuing authority so that anyone can verify that the certificate is real.


 

Digital Certificates

A digital certificate is an electronic "credit card" that establishes your credentials when doing business or other transactions on the Web. It is issued by a certification authority (CA), containing your name, a serial number, expiration dates, a copy of the certificate holder's public key (used for encrypting and decrypting messages and digital signatures), and the digital signature of the certificate-issuing authority so that a recipient can verify that the certificate is real. Some digital certificates conform to a standard, X.509. Digital certificates can be kept in registries so that authenticated users can look up other users' public keys.

 

eCommerce

Business transactions conducted over the Internet, Intranet in digital form.


 

Encryption

The transformation of plaintext into an apparently less readable form (called ciphertext) through a mathematical process. The ciphertext may be read by anyone who has the key that decrypts (undoes the encryption) the ciphertext.

The key is fundamental to the strength of the encryption. You need the one correct key before you can decrypt the ciphertext. It follows, then, that the longer is the key, the greater is the range of possible values it could have. The range of possible values is called the key space. The greater the key space, the more difficult it is for an unauthorized person to discover the correct key.

Encryption cannot make unauthorized decryption impossible; it can merely make it improbable. With unlimited processing capacity and unlimited time available, all cryptosystems could be broken. The purpose of encryption is to make it as unlikely as possible that a ciphertext could be broken within the period of time during which the contents should remain secret.

There is an arbitrary and subjective distinction between weak and strong encryption. Strong encryption implies that it would effectively be impossible to find the key within the effective lifetime of the secret. Any key length above 56 bits is generally considered to be 'strong' encryption.


 

FIPS

Federal Information Processing Standards. See NIST.


 

Hash Function

A function that takes a variable sized input and has a fixed size output.


 

Hashing

An iterative process that computes a value (i.e., the 'hash word' or 'message digest') from data. Hashing is a one-way process. It is simple to produce a hash value from a string of data, but it is effectively impossible to compute the original string from the hash value.


 

Integrity

One of the four fundamental requirements of information security, integrity measures are meant to protect data and/or resources from unauthorized modification. Data whose integrity has failed is said to be corrupted.

 

IPSec/IKE

IPSec (Internet Protocol Security) is a developing standard for security at the network or packet-processing layer of network communication. Earlier security approaches have inserted security at the application layer of the communications model. IPSec will be especially useful for implementing virtual private networks and for remote user access through dial-up connection to private networks. A big advantage of IPSec is that security arrangements can be handled without requiring changes to individual user computers. Cisco has been a leader in proposing IPSec as a standard (or combination of standards and technologies) and has included support for it in its network routers.

IPSec provides two choices of security service: Authentication Header (AH), which essentially allows authentication of the sender of data, and Encapsulating Security Payload (ESP), which supports both authentication of the sender and encryption of data as well. The specific information associated with each of these services is inserted into the packet in a header that follows the IP packet header. Separate key protocols can be selected, such as the ISAKMP/Oakley protocol.


 

Key

A string of bits used widely in cryptography, allowing people to encrypt and decrypt data; a key can be used to perform other mathematical operations as well. Given a cipher, a key determines the mapping of the plaintext to the ciphertext. See also distributed key, private key, public key, secret key, session key, shared key, sub key, symmetric key, weak key.


 

Key Escrow

Key escrow involves lodging the decryption key with a Trusted Third Party (TTP). It is an emotive subject because of governments' repeated attempts and known desire to enforce a general requirement not merely for key escrow, but also for the mandatory release of that key to Law Enforcement agencies. Nevertheless, key escrow is a concept that will need to be considered by many organizations. If strong encryption is used, and the relevant key is lost either through accident or misadventure, theft or employee disaffection, then the organization concerned will lose its data. Lodging the key with a TTP means that it can be recovered in extremis.

The security issues center around the security of the TTP. In general, any addition to the chain of trust is the addition of a weak link in the chain. Use of a TTP introduces new threats that would not otherwise exist: TTP staff could be duped, bribed or threatened; TTP systems could be hacked.



 

Key File

Some encryption programs store your encryption keys in a file where they can be conveniently accessed. Usually, the keys are themselves strongly encrypted -- this means that you need to enter a pass phrase to begin using the key file, but you do not then need to enter each key as it is used. This helps ensure that if your key file is stolen, it will be of limited use to the attacker. Even so, you are advised not to store key files on your hard disk because of the risk of compromise.

 

Key Management

Key management is the administrative side of cryptography, and is one of the biggest problems faced by any crypto system. It involves the generation, certification, distribution and revocation of keys - all of which must be done in a secure manner. It can be undertaken manually, by software, or by outsourcing to a third party such as a Certification Authority. It is the difficulties of key management that make the one unbreakable crypto system, the One Time Pad, unrealistic for the commercial market.

 

Key Pair

The full key information in a public-key cryptosystem, consisting of the public key and private key.


 

Key Space

The name given to the range of possible values for a cryptographic key. Normally described in terms of bits, as in the number of bits needed to count every distinct key. The longer the key length (in bits), the greater the key space (the range of possible key values doubles for every 'bit' added).

A brute force attack will on average require 50% of all possible keys to be guessed before the correct key is found. The key space is consequently used as a simple measure to describe the strength of the cryptosystem. A 64-bit key space is no longer considered sufficient to defeat a brute force attack. A 120-bit key space is often considered to be the requirement.


 

MD5

A Message Digest algorithm, frequently used alongside encryption and authentication software. MD5 produces a short (typically 16 bytes) checksum of a file. Any change to the original file will result in a change to the checksum and thus allow tampering to be detected without having to compare the full-length files.

 

NIST

National Institute of Standards and Technology, a United States agency that produces security and cryptography related standards (as well as others); these standards are published as FIPS documents.


 

Non-repudiation

The process by which the sender of data is provided with proof of delivery, and the receiver is assured of the sender's identity. This is non-repudiation, so that neither party can deny either sending or receiving the data in question. It provides a sound framework, and is considered vital, for the future development of electronic commerce.

Unfortunately, genuine non-repudiation would seem to be beyond our current capabilities. It can only be achieved by protecting the key holder?s private key from theft, and protecting the computer that uses that private key from infiltration or subversion. Most experts agree that neither of these are, or are likely to become in the foreseeable future, realizable.


 

PAP

Password Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access, but merely identifies the remote end. The router or access server then determines if that user is allowed access. PAP is supported only on PPP lines. Compare with CHAP.

 

Pass Phrase

A password constructed of more than one word.


 

Password

A security device consisting of a protected/private string of characters known only to the authorized user/s and the system. It is used to authenticate the authorized user of a computer or data file.

 

Password Sniffing

The use of a sniffer to capture passwords as they pass across a network. The network could be a local area network, or the Internet itself. The sniffer could be hardware (if the attacker has physical access to the network) or software (in which case all that is required is the ability to compromise a server). A favorite method for 'installing' a password sniffer onto a local area network would be through the use of a ?Trojan horse? virus application.

Once a LAN has been compromised, it is very difficult to detect the sniffer. The LAN is likely to be Ethernet - in which case the attacker ensures that the compromised server is placed into 'promiscuous' mode (that is, able to receive all the packets on the network rather than those specifically addressed to it). When the sniffer sees a packet that fits certain criteria, it logs it to a file. The most common criteria for an interesting packet are those contains words like "login" or "password".

But the sniffer itself is passive. It doesn't change anything: it just listens and logs, allowing the attacker to analyze the logs later. Since it doesn't change anything, it is difficult to detect. But the log itself could grow very large - so the detection of such logs could demonstrate the existence of a sniffer.

The only safe defense against sniffers is constantly changing your passwords.


 

PC/SC

The PC/SC standard (PC/Smartcard) was developed by Microsoft - in conjunction with other IT companies - to ensure compatibility between smart cards, card reader/writers and computers produced by different manufacturers. This initiative requires manufacturers of smart card readers and smart card manufacturers to develop the relevant drivers and service programs for their hardware. Thus PC/SC became established as the standard for the chip card industry.

The PC/SC standard development was based on the current ISO 7816 standard for smart card communications, and supports business-specific application standards such as EMV (Europay, MasterCard, Visa) and GSM (Global Standard for Mobile Communication).


 

PGP

Pretty Good Privacy. An encryption program for encrypting data files and/or e-mail messages on PCs and Macs. Considered to be among the strongest encryption utilities available.

PGP also has facilities for authentication, so that you can be sure a message was really sent by the person who it appears to be from, and non-repudiation to prevent someone from denying that they ever sent a message.



 

PKI (Public Key Infrastructure)

PKI is the term given to the overall system required to provide public key encryption and digital signature services. The purpose of the PKI is thus to manage keys and certificates, and thereby establish and maintain a trustworthy networking environment.



 

PKCS#11

PKCS (Public-Key Cryptography System) is a set of informal inter-vendor standard protocols developed by RSA for making possible secure information exchange on the Internet. The standards include RSA encryption, password-based encryption, extended certificate syntax, and cryptographic message syntax for S/MIME, RSA's proposed standard for secure e-mail.

This standard specifies an API, called Cryptoki, to devices, which hold cryptographic information and perform cryptographic functions. Cryptoki, pronounced crypto-key and short for cryptographic token interface, follows a simple object-based approach, addressing the goals of technology independence (any kind of device) and resource sharing (multiple applications accessing multiple devices), presenting to applications a common, logical view of the device called a cryptographic token.

Plaintext

Data that has not been encrypted, or ciphertext that has been decrypted.


 

Private Key

The undis d key in a matched key pair (that is, the private key and the public key) that each party safeguards for public key cryptography.


 

Private Key Cryptography

Synonymous with Symmetric Cryptography. Encryption where the same key is used to both encrypt and decrypt data. This can cause problems unless a secure method can be found for transferring the key along with the encrypted data.


 

Public Key

A public key is a value provided by some designated authority as a key that, combined with a private key, can be used to effectively encrypt and decrypt messages and digital signatures. The use of combined public and private keys is known as asymmetric cryptography. A system for using public keys is called a public key infrastructure (PKI).

 

Public Key Cryptography

Synonymous with Asymmetric Cryptography. An encryption system developed by Whitfield Diffie and Martin Hellman that uses two keys; one public and one private. Anyone can know a person's public key; no one should ever know a person's private key. Encrypted messages may be sent to a recipient by using that person's public key. However, the message can only be decrypted by the associated private key. In this way, decryption keys need never be published nor transmitted.


 

Radius (Remote Authentication Dial-In User Service)

The Remote Authentication Dial-In User Service (RADIUS) is a client/server security protocol created by Lucent InterNetworking Systems. RADIUS is an Internet draft standard protocol. User profiles are stored in a central location, known as the RADIUS server. RADIUS clients communicate with the RADIUS server to authenticate users. The server specifies back to the client what the authenticated user is authorized to do. Although the term RADIUS refers to the network protocol that the client and server use to communicate, it is often used to refer to the entire client/server system.


 

RAS (Remote Access System)

Remote access is the ability to get access to a computer or a network from a remote distance. In corporations, people at branch offices, telecommuters, and people who are traveling may need access to the corporation's network. Home users get access to the Internet through remote access to an Internet service provider (ISP). Dial-up connection through desk, notebook, or handheld computer modems over regular telephone lines is a common method of remote access. Remote access is also possible using a dedicated line between a computer or a remote local area network and the "central" or main corporate local area network.


 

Risk Management

The total process of identifying, controlling, and eliminating or minimizing uncertain events that may affect system resources. It includes risk analysis, cost-risk analysis, selection, implementation and test, security evaluation of safeguards, and overall security review.

 

RSA

A public key encryption algorithm invented by Messrs Rivest, Shamir and Adelman of IBM. "RSA is a public-key cryptosystem for both encryption and authentication; it was invented in 1977 by Ron Rivest, Adi Shamir, and Leonard Adelman. It works as follows: take two large primes, p and q, and find their product n = pq; n is called the modulus. Choose a number, e, less than n and relatively prime to (p-1)(q-1), which means that e and (p-1)(q-1) have no common factors except 1. Find another number d such that (ed - 1) is divisible by (p-1)(q-1). The values e and d are called the public and private exponents, respectively. The public key is the pair (n,e); the private key is (n,d). The factors p and q maybe kept with the private key, or destroyed. "It is difficult (presumably) to obtain the private key d from the public key (n,e). If one could factor n into p and q, however, then one could obtain the private key d. Thus the security of RSA is related to the assumption that factoring is difficult."

 

S/MIME

S/MIME (Secure Multi-Purpose Internet Mail Extensions) is a secure method of sending e-mail that uses the RSA encryption system. S/MIME is included in the latest versions of the Web browsers from Microsoft and Netscape and has also been endorsed by other vendors that make messaging products. RSA has proposed S/MIME as a standard to the Internet Engineering Task Force (IETF). An alternative to S/MIME is PGP/MIME, which has also been proposed as a standard.

MIME itself, described in the IETF standard called RFC 1521, spells out how an electronic message will be organized. S/MIME describes how encryption information and a digital certificate can be included as part of the message body. S/MIME follows the syntax provided in the Public-Key Cryptography Standard (PKCS) format #7.


 

SDK

Short for software development kit, the SDK is a programming package that enables a programmer to develop applications for a specific platform. Typically an SDK includes one or more APIs, programming tools, and documentation.

The eToken Software Developer's Kit (SDK) v1.25 allows developers to create customized security applications and integrate a web-based method for eToken driver deployment across the enterprise. The SDK includes eToken development information and APIs to establish interfaces with applications or services designed to support Aladdin's R2 eToken.
The eToken SDK uses standard security interfaces (including PC/SC, PKCS#11 and CAPI), ties the eToken to access control and VPN solutions, and gives full support for Public Key Infrastructure (PKI). It also includes drivers and support for: Windows 98, NT4.0, and Windows 2000.


 

Security Clearance

Assuming that a system's objects (let us say, 'files') are all given an hierarchical label defining their sensitivity (Security Classification), a subject's (let us say, user's) security clearance is the corresponding label that defines the degree of sensitivity that can be accessed. Clearance level labels could, and for administrative ease possibly should, be given the same names as classification level labels. Under such circumstances, a user with a clearance level up to 'secret' would be able to access files with an classification level up to, but not higher than, 'secret'.



 

Session Key

A key for symmetric-key cryptosystems, which is used for the duration of one message or communication session


 

Single Sign-on

The ability to log in into multiple computers or servers with a single action and the entry of a single password. Especially useful where, for example, a user on a LAN or WAN requires access to a number of different servers. Although single sign-on makes the login process more convenient for the user, it does mean that the password becomes more valuable to a hacker because of the large number of systems it can access. For this reason some consultants discourage the use of single sign-on systems, and, where there is no other realistic option, recommend that passwords are guarded safely and changed regularly. Users must also be made fully aware of their responsibility for safeguarding their password.

 

SSL

SSL (Secure Sockets Layer) is a program layer created ??? for managing the security of message transmissions in a network. The idea is that the programming for keeping your messages confidential ought to be contained in a program layer between an application (such as your Web browser or HTTP) and the Internet's TCP/IP layers. The "sockets" part of the term refers to the sockets method of passing data back and forth between a client and a server program in a network or between program layers in the same computer. SSL uses the public-and-private key encryption system from RSA, which also includes the use of a digital certificate.


 

Strong Encryption

A term given to describe a cryptosystem that uses a key of sufficient length that it becomes effectively impossible to 'break' the cipher within a meaningful time frame.


 

Symmetric Cryptography

See Private Key Cryptography

 

Triple DES (3-DES) Encryption

Triple DES is a method of data encryption that uses the same block size and can use the same hardware as DES; it just uses three keys and runs DES three times (encrypting each block with the first key, decrypting it with the second, then encrypting it with the third). The strength of Triple-DES is substantially stronger than DES.


 

Tamper Evident

A feature providing assurance that can identify if something has changed or been tampered with.

 

Tamper Resistant

In cryptographic terms, this usually refers to a hardware device that is either impossible or extremely difficult to reverse engineer or extract information from.


 

Trusted Third Party (TTP)

A trustworthy organization such as a bank, or specialist consultancy, which provides security-related services that enable transactions such as encryption, and authentication to be conducted securely. Under various schemes being implemented or proposed by a number of governments throughout Europe and the world, companies who use strong encryption will be required to lodge copies of their encryption keys with a trusted third party in order that the keys can be divulged to law enforcements groups such as those investigating organized crime, drugs or terrorism.

 

Username / User ID

A unique "name" by which each user is known to the system. This name is assigned to each user whenever they register to use the system.


 

Verification

The act of recognizing that a person or entity is who or what it claims to be.


 

VPN

A virtual private network (VPN) is a private data network that makes use of the public telecommunication infrastructure, maintaining privacy through the use of a tunneling protocol and security procedures. A virtual private network can be contrasted with a system of owned or leased lines that can only be used by one company. The idea of the VPN is to give the company the same capabilities at much lower cost by using the shared public infrastructure rather than a private one. Phone companies have provided secure shared resources for voice messages. A virtual private network makes it possible to have the same secure sharing of public resources for data. Companies today are looking at using a private virtual network for both extranets and wide-area intranets.

Using a virtual private network involves encrypting data before sending it through the public network and decrypting it at the receiving end. An additional level of security involves encrypting not only the data but also the originating and receiving network addresses. Microsoft, 3Com, and several other companies have developed the Point-to-Point Tunneling Protocol (PPTP) and Microsoft has extended Windows NT to support it. VPN software is typically installed as part of a company's firewall server.

 

X.509 Certificate Version 3

Application of public key technology requires the user of a public key to be confident that the public key belongs to the correct remote subject (person or system) with which an encryption or digital signature mechanism will be used. This confidence is obtained through the use of public key certificates, which are data structures that bind public key values to subject identities. The binding is achieved by having a trusted certification authority (CA) digitally sign each certificate. A certificate has a limited valid lifetime, which is indicated in its signed contents. Because a certificate-using client can independently check a certificate?s signature and timeliness, certificates can be distributed via non-trusted communications and server systems, and can be cached in unsecured storage in certificate-using systems.

The standard known as ITU-T X.509 (formerly CCITT X.509) or ISO/IEC 9594-8, which was first published in 1988 as part of the X.500 Directory recommendations, defines a standard certificate format.

The main reason for the structural restrictions imposed by RFC 1422 was the restricted certificate format provided with X.509 v1. With X.509 v3, most of the requirements addressed by RFC 1422 can be addressed using certificate extensions, without a need to restrict the CA structures used. In particular, the certificate extensions relating to certificate policies obviate the need for PCAs and the constraint extensions obviate the need for the name subordination rule.

In response to these new requirements, ISO/IEC and ANSI X9 developed the X.509 version 3 (v3) certificate format. The v3 format extends the v2 format by adding provision for additional extension fields. Particular extension field types may be specified in standards or may be defined and registered by any organization or community. In June 1996, standardization of the basic v3 format was completed [X.509-AM].

ISO/IEC and ANSI X9 have also developed a set of standard extensions for use in the v3 extensions field [X.509-AM]. These extensions can convey such data as additional subject identification information, key attribute information, policy information, and certification path constraints.

However, the ISO/IEC and ANSI standard extensions are very broad in their applicability. In order to develop interoperable implementations of X.509 v3 systems for Internet use, it is necessary to specify a profile for use of the X.509 v3 extensions tailored for the Internet. For example the Internet Public Key Infrastructure (IETF-PKIX) working group [PKIX] has specified a profile for Internet WWW, electronic mail, and IPSEC applications. Environments with additional requirements may build on this profile or may replace it.