安全电子交易协议
(secure Electronic Transaction简称SET) 由威士(VISA)国际组织、万事达(MasterCard)国际组织创建，结合IBM、Microsoft、Netscope、GTE等公司制定的电子商务中安全电子交易的一个国际标准。其主要目的是解决信用卡电子付款的安全保障性问题，这包括：保证信息的机密性，保证信息安全传输，不能被窃听，只有收件人才能得到和解密信息；保证支付信息的完整性，保证传输数据完整接收，在中途不被篡改；认证商家和客户，验证公共网络上进行交易活动包括会计机构的设置、会计人员的配备及其职责权利的履行和会计法规、制度的制定与实施等内容。合理、有效地组织会计I作，意义重大，它有助于提高会计信息质量，执行国家财经纪律和有关规定；有助于提高经济效益，优化资源配置。会计工作的组织必须合法合规。讲求效益，必须建立完善的内部控制制度，必须有强有力的组织保证。
英文原文：
People today pay for online purchases by sending their credit card details to the merchant. A protocol such as SSL or TLS keeps the card details safe from eavesdroppers, but does nothing to protect merchants from dishonest customers or vice-versa. SET addresses this situation by requiring cardholders and merchants to register before they may engage in transactions. A cardholder registers by contacting a certificate authority, supplying security details and the public half of his proposed signature key. Registration allows the authorities to vet an applicant, who if approved receives a certificate confirming that his signature key is valid. All orders and confirmations bear digital signatures, which provide authentication and could potentially help to resolve disputes.
A SET purchase involves three parties: the cardholder, the merchant, and the payment gateway (essentially a bank). The cardholder shares the order information with the merchant but not with the payment gateway. He shares the payment information with the bank but not with the merchant. A set dual signature accomplishes this partial sharing of information while allowing all parties to confirm that they are handling the same transaction. The method is simple: each party receives the hash of the withheld information. The cardholder signs the hashes of both the order information and the payment information. Each party can confirm that the hashes in their possession agrees with the hash signed by the cardholder. In addition, the cardholder and merchant compute equivalent hashes for the payment gateway to compare. He confirms their agreement on the details withheld from him.
All parties are protected. Merchants do not normally have access to credit card numbers. Moreover, the mere possession of credit card details does not enable a criminal to make a SET purchase; he needs the cardholder’s signature key and a secret number that the cardholder receives upon registration. The criminal would have better luck with traditional frauds, such as ordering by telephone. It is a pity that other features of SET (presumably demanded by merchants) weaken these properties. A merchant can be authorized to receive credit card numbers and has the option of accepting payments given a credit card number alone.
SET is a family of protocols. The five main ones are cardholder registration, merchant registration, purchase request, payment authorization, and payment capture. There are many minor protocols, for example to handle errors. SET is enormously more complicated than SSL, which merely negotiates session keys between the cardholder’s and merchant’s Internet service providers. Because of this complexity, much of which is unnecessary, the protocol is hardly used. However, SET contains many features of interest:
The model is unusual. In the registration protocols, the initiator possesses no digital proof of identity. Instead, he authenticates himself by filing a registration form whose format is not specified. Authentication takes place outside the protocol, when the cardholder’s bank examines the completed form.
The dual signature is a novel construction. The partial sharing of information among three peers leads to unusual protocol goals.
SET uses several types of digital envelope. A digital envelope consists of two parts: one, encrypted using a public key, contains a fresh symmetric key K and identifying information; the other, encrypted using K, conveys the full message text. Digital envelopes keep public-key encryption to a minimum, but the many symmetric keys complicate the reasoning. Most verified protocols distribute just one or two secrets.