base64传输编码的使用场合

一直不是太明白,base64的使用场合，感觉主要是用于传输内容的非明文传输.
但事实上还有很多情境，需要用到，下面是baidu百科和wikipedia的相关说明。
请有过相关base64编码的J友，说一下大家的实际的使用场合经验.

http://baike.baidu.com/view/469071.htm
From http://en.wikipedia.org/wiki/Base64
http://stackoverflow.com/questions/201479/what-is-the-use-of-base-64-encoding

"The term Base64 refers to a specific MIME content transfer encoding. It is also used as a generic term for any similar encoding scheme that encodes binary data by treating it numerically and translating it into a base 64 representation. The particular choice of base is due to the history of character set encoding: one can choose a set of 64 characters that is both part of the subset common to most encodings, and also printable. This combination leaves the data unlikely to be modified in transit through systems, such as email, which were traditionally not 8-bit clean."

"Base64 can be used in a variety of contexts:

Evolution and Thunderbird use Base64 to obfuscate e-mail passwords[1]
Base64 can be used to transmit and store text that might otherwise cause delimiter collision

Base64 is often used as a quick but insecure shortcut to obscure secrets without incurring the overhead of cryptographic key management
Spammers use Base64 to evade basic anti-spamming tools, which often do not decode Base64 and therefore cannot detect keywords in encoded messages.

Base64 is used to encode character strings in LDIF files
Base64 is sometimes used to embed binary data in an XML file, using a syntax similar to ...... e.g. Firefox's bookmarks.html.

Base64 is also used when communicating with government Fiscal Signature printing devices (usually, over serial or parallel ports) to minimize the delay when transferring receipt characters for signing.
Base64 is used to encode binary files such as images within scripts, to avoid depending on external files.
Can be used to embed raw image data into a CSS property such as background-image."

一句话：二进制转ascii

特定：把看不见的转换成看得见的
缺点：会增加长度

页面间传递二进制数据时
数字证书等信息安全

顶你

我在想，如何改OS的底层，可以把非可见字符以一个特定的符号显示 比如178 显示西格马

很好，不过我一般都是明文给的