说明：BASE64不是用来加密的。你看看经过BASE64编码后的字符串，全部都是由标准键盘上面的常规字符组成，这样编码后的字符串在网关之间传递不会产生UNICODE字符串不能识别或者丢失的现象。你再仔细研究下EMAIL就会发现其实EMAIL就是用base64编码过后再发送的。然后接收的时候再还原。
还有一种情况下用BASE64编码也很好，比如一个图片文件，或者其他任何二进制文件。我可以把它编码成字符串。这样用XML或者数据库就能直接以文本的方式来存储这些文件了。
<pre id="answer-content-418531940" class="answer-text mb-10" name="code" style="white-space: pre-wrap; word-wrap: break-word; margin-top: 0px; margin-bottom: 10px; padding: 0px; font-family: arial, 'courier new', courier, 宋体, monospace; background-color: rgb(255, 255, 255);">base64是一种编码方式，编码算法完全公开，所以逆向解码即可
</pre><pre id="best-content-419398544" class="best-text mb-10" name="code" style="white-space: pre-wrap; word-wrap: break-word; margin-top: 0px; margin-bottom: 10px; padding: 0px; font-family: arial, 'courier new', courier, 宋体, monospace; color: rgb(51, 51, 51); line-height: 24px; background-color: rgb(241, 254, 221);"><p style="margin-top: 0px; margin-bottom: 0px; padding-top: 0px; padding-bottom: 0px; font-family: Arial; line-height: 26px;">使用GTMBase64需要在工程中加入三个文件</p><div class="cnblogs_code" style="font-family: Arial; line-height: 26px;"><pre style="white-space: pre-wrap; word-wrap: break-word;"><a target=_blank href="http://code.google.com/p/google-toolbox-for-mac/source/browse/trunk/GTMDefines.h?r=87" target="_blank" style="color: rgb(255, 153, 0); text-decoration: none;">GTMDefines.h</a> <a target=_blank href="http://code.google.com/p/google-toolbox-for-mac/source/browse/trunk/Foundation/GTMBase64.h?r=87" target="_blank" style="color: rgb(255, 153, 0); text-decoration: none;">GTMBase64.h</a> <a target=_blank href="http://code.google.com/p/google-toolbox-for-mac/source/browse/trunk/Foundation/GTMBase64.m?r=87" target="_blank" style="color: rgb(255, 153, 0); text-decoration: none;">GTMBase64.m</a> 你可以在这里找到这三个文件 <a target=_blank href="http://code.google.com/p/google-toolbox-for-mac/source/browse/trunk/Foundation/?r=87" style="color: rgb(255, 153, 0); text-decoration: none;">http://code.google.com/p/google-toolbox-for-mac/source/browse/trunk/Foundation/?r=87</a>
<p style="margin-top: 0px; margin-bottom: 0px; padding-top: 0px; padding-bottom: 0px; font-family: Arial; line-height: 26px;">示例代码：</p><div class="cnblogs_code" style="font-family: Arial; line-height: 26px;"><div class="cnblogs_code_toolbar"><span class="cnblogs_code_copy"><a target=_blank title="复制代码" style="color: rgb(255, 153, 0);"><img src="http://common.cnblogs.com/images/copycode.gif" alt="复制代码" style="border: none; max-width: 100%;" /></a></span></div><pre style="white-space: pre-wrap; word-wrap: break-word;"><span style="color: rgb(0, 0, 255);">#import</span> <span style="color: rgb(128, 0, 0);">"</span><span style="color: rgb(128, 0, 0);">GTMBase64.h</span><span style="color: rgb(128, 0, 0);">"</span>
- (<span style="color: rgb(0, 0, 255);">void</span>)testExample
{
NSData *data = [<span style="color: rgb(128, 0, 0);">@"</span><span style="color: rgb(128, 0, 0);">HelloWorld</span><span style="color: rgb(128, 0, 0);">"</span> dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];
NSString* encoded = [[NSString alloc] initWithData:[GTMBase64 encodeData:data] encoding:NSUTF8StringEncoding];
NSLog(<span style="color: rgb(128, 0, 0);">@"</span><span style="color: rgb(128, 0, 0);">encoded:%@</span><span style="color: rgb(128, 0, 0);">"</span>, encoded);
NSString* decoded = [[NSString alloc] initWithData:[GTMBase64 decodeString:encoded] encoding:NSUTF8StringEncoding];
NSLog(<span style="color: rgb(128, 0, 0);">@"</span><span style="color: rgb(128, 0, 0);">decoded:%@</span><span style="color: rgb(128, 0, 0);">"</span>, decoded);
[encoded release];
[decoded release];
}
输出：
2012-04-10 12:13:10.121 fs_test[7370:b603] encoded:SGVsbG9Xb3JsZA== 2012-04-10 12:13:10.122 fs_test[7370:b603] decoded:HelloWorld
</pre><pre id="best-content-419398544" class="best-text mb-10" name="code" style="white-space: pre-wrap; word-wrap: break-word; margin-top: 0px; margin-bottom: 10px; padding: 0px; font-family: arial, 'courier new', courier, 宋体, monospace; color: rgb(51, 51, 51); line-height: 24px; background-color: rgb(241, 254, 221);">使用示例：
引入头文件：
#import "GTMBase64.h"
UIImage *image;
NSData *data= UIImagePNGRepresentation(image);
if([data length]>0){
data = [GTMBase64 encodeData:data]; //编码
}
if([data length]>0){
data = [GTMBase64 decodeData:data]; //解码
}
