AWS Signer causes large OTA file size / object size increase

Question

When using AWS Signer to sign an AWS IoT OTA update, how much bigger should I expect the signed binary to be?  
The file size / object size of the signed binary in S3 is much larger than the unsigned binary.  
I'm signing using the following AWS CLI command:  
$ aws signer start-signing-job   
--source 's3={bucketName=my_OTA_bucket,key=my_OTA_binary.bin,version=my_latest_version_GUID}'  
--destination 's3={bucketName=my_OTA_bucket,prefix=signed-}'  
--profile-name my_code_signing_profile  
  
How many KB should I expect the AWS Signer to add to the resulting OTA binary?  
  
-Brant

Answer

I discovered the increase in size caused by AWS Signer is expected and only affects the size of signed S3 object and the signed object in transport.  
  
The raw binary size of the OTA on the IoT thing is not affected.  
  
The signed binary is stored as JSON with the raw payload binary encoded in text, resulting in the increase in file size.  
The signed JSON file is comprised of "rawPayloadSize", "signature", "signatureAlgorithm" description and  
a "payload" text encoding of the binary.  
  
When it reaches the thing, the encoded binary's signature is checked and the payload is converted into the original OTA binary file.  
  
-Brant

AWS Signer causes large OTA file size / object size increase

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