如何将JSON对象转换为base64字符串？

我正在尝试遵循Amazon 使用POST将基于浏览器的文件上传到S3 的示例。

该示例提供了此JSON策略...

{ "expiration": "2013-08-06T12:00:00.000Z",
  "conditions": [
    {"bucket": "examplebucket"},
    ["starts-with", "$key", "user/user1/"],
    {"acl": "public-read"},
    {"success_action_redirect": "http://acl6.s3.amazonaws.com/successful_upload.html"},
    ["starts-with", "$Content-Type", "image/"],
    {"x-amz-meta-uuid": "14365123651274"},
    ["starts-with", "$x-amz-meta-tag", ""],

    {"x-amz-credential": "AKIAIOSFODNN7EXAMPLE/20130806/us-east-1/s3/aws4_request"},
    {"x-amz-algorithm": "AWS4-HMAC-SHA256"},
    {"x-amz-date": "20130806T000000Z" }
  ]
}

...并说这是该策略的base64编码版本：

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

但是，当我从Node.js REPL执行此操作时...

var policy = {
  "expiration": "2013-08-06T12:00:00.000Z",
  "conditions": [
    {"bucket": "examplebucket"},
    ["starts-with", "$key", "user/user1/"],
    {"acl": "public-read"},
    {"success_action_redirect": "http://acl6.s3.amazonaws.com/successful_upload.html"},
    ["starts-with", "$Content-Type", "image/"],
    {"x-amz-meta-uuid": "14365123651274"},
    ["starts-with", "$x-amz-meta-tag", ""],

    {"x-amz-credential": "AKIAIOSFODNN7EXAMPLE/20130806/us-east-1/s3/aws4_request"},
    {"x-amz-algorithm": "AWS4-HMAC-SHA256"},
    {"x-amz-date": "20130806T000000Z" }
  ]
};

console.log(new Buffer(JSON.stringify(policy)).toString('base64'));

...我得到了不同的base64字符串：

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

我是在做错什么，还是亚马逊的示例中有错误？