utils, tools, httr, xml2 (> 1.0.0), base64enc, digest,
aws.signature (>= 0.2.6)
utils, tools, httr, xml2 (> 1.0.0), base64enc, digest,
aws.signature (>= 0.3.7)
utils, tools, curl, httr, xml2 (> 1.0.0), base64enc, digest,
aws.signature (>= 0.3.7)