Summary
AWS4-HMAC-SHA256, also known as Signature Version 4 or Sig v4, is an authentication mechanism supported by Amazon Simple Storage Service (Amazon S3).
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It is used to provide authentication of requests by including the algorithm used to calculate the signature, access key ID and scope information, a semicolon-separated list of request headers, and a 256-bit signature in the Authorization header value.
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Sig v4 is supported by all AWS regions, while some regions also support the older Sig v2.
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According to
