推荐回答（3个）
信用卡号：
3开头是日本JCB和美国AMERICANEXPRESS。
4开头是国际品牌VISA信用卡（世界第一信用卡组织）
5开头是国际品牌MASTERCARD。
6开头的是中国银联单币卡（或者美国discover）。
CVV码：
VISA卡的安全码叫做CVV2（Card Verification Value 2），有3位数字，平印在信用卡背面签名栏上卡号后4位处。
万事达卡（MarsterCard）的安全码叫做CVC2（Card Validation Code 2），有3位数字，平印在信用卡背面签名栏上卡号后4位处。
发现卡（Discover Card）的安全码叫做Cardmember ID，有3位数字，平印在信用卡背面签名栏上。
运通卡（American Express）的安全码叫做CID（Card Identification Number），有4位数字，平印在信用卡正面信用卡卡号上方。
JCB卡（Japan Credit Bureau）的安全码叫做CAV2（ Card Authentication Value 2），有3位数字，平印在信用卡背面签名栏上卡号后4位处。
CVV，即 Card Verification Value，而Mastercard 称作Card Validation Code (CVC)。VISA CVV和MC CVC都是由卡号、有效期和服务约束代码生成的3位或4位数字，一般写在卡片磁条的2磁道用户自定义数据区里面。
【技术原理】：
“Visa验证”服务基于名为 “三维安全”的技术平台上，这种技术的规格和通信协议是采用加密安全连接层协议(SSL)技术加密，这种加密技术现为大多数网上商户所采纳。
“Visa验证”服务标志会显示在参与服务的网上商户的网页上，也会在持卡人登记、以及每次网上购物输入个人密码验证时出现。
VISA验证的作用就是，不仅可以验证境外网站的合法性，还可验证持卡人身份，从而降低了境外网上购物被盗用的风险。
您好，CVV / CVC码是印在您信用卡卡片上的一组检查码，一般为3位或4位。如果您有小额贷款的需求，推荐您使用有钱花，“有钱花”是原百度金融信贷服务品牌（原名：百度有钱花，2018年6月更名为“有钱花”）， 具有申请简便、放款快、借还灵活、息费透明、安全性强等特点。申请材料简单，最快30秒审批，最快3分钟放款。可提前还款，还款后恢复额度可循环借款。希望这个回答对您有帮助，手机端点击下方，立即测额！最高可借额度20万。
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