Amazon S3 Transfer Manager directory upload - Hashes - java

Currently, We implement S3 individual file uploads by adding MD5 hashes to the upload request to validate our file transfer. But now we want to leverage AWS S3 Transfer Manager for directory upload. So, now how to check for Hashes of the folders/files uploaded?
I have scouted through the documentation available on Transfer Manager but couldn't find any information on Hashes.

I believe the SDK has already taken care of that for you. The AWS Signature Version 4 calculation includes the SHA256 of the payload. [ref]

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What's the best approach to verify integrity for crypted files on AWS EFS?

Hello i'm working for the first time with AWS EFS, and for security reasons in my organization data will be stored encrypted, but not with AWS standard EFS encryption.
For each upload request, encryption keys are collected via a VPN, encrypt the binary and than store file on EFS.
Each upload part must not exceed 200MB, and all parts must be merged at the end of the upload.
I'm looking for the best approach to make things a litle bit easy in a complicated architecture,
so what's the best approach to verify integriry ?:
Uploaded file is as same as received on server side
Loaded EFS file is as same as stored
Thanks.

Upload content to AWS S3 and serve the content via Cloudfront

I need to upload static contents like image to AWS S3 and provide a link back so that image can be accessed through Cloudfront CDN (content delivery network). I am new to AWS and I read that s3 bucket is linked to CDN and I believe it's all configuration based. From java code I am able to upload to s3 and get the bucket based url back. How can I retrieve CDN url from java code for the same uploaded image. Could you please help me out here.
The AWS S3 has to be manually linked to AWS CloudFront (Image attached).
Once a Distribution is created, you can see a new domain mapped to the distribution. Using that domain name you should be able to access the CDN URL in your Java code.

Send attachments on mail from S3 bucket using Java

I want to send attachments (files from S3 bucket) in a mail triggered to users. How can be this done using Java?
I haven't tried though.
If file size greater then I would suggest to create presigned URL for files and share them via mail.
If files are too short in size, better to go with download and attach.
reference: https://docs.aws.amazon.com/AmazonS3/latest/dev/ShareObjectPreSignedURLJavaSDK.html

How to archive files revision-safe using java?

I am searching for a way to archive files in a revision-save way.
I imagine a java based rest service, to pass a file, which is then unchangeable stored and accessible via an URI.
How could I implement something like this? Is a Hadoop Archive a possible building block? Or is this only possible using a Content-Addressed Storage?
I think the best solution is to compute a checksum for each file and return the ID of the file together with the checksum as a combined access URL. Than each time a client requests a file via the URL (including the checksum), the service verifies the checksum again and can so garantie, that the file returned was not modified from the point of time when the file was stored and is identical to the version the client expect. The URL is the surety of the immutability of the requested file.
Also the client can verify the checksum if the client did not trust the service.

JetS3t and Server Side Encryption with Customer-Provided Keys

I'm exploring an option to store encrypted data to S3. My backend is build with Java and I'm already using JetS3t library for some simple S3 storage manipulations. So, my question is: How to use JetS3t with S3's Server Side Encryption with customer-provided keys (SSE-C) to store files in encrypted format on S3?
I tried to look through the Programmer's Guid for JetS3t but didn't find anything concrete in that regards.
According to the docs here http://docs.aws.amazon.com/AmazonS3/latest/dev/ServerSideEncryptionCustomerKeys.html, you need to add the following headers in your request:
x-amz-server-side​-encryption​-customer-algorithm Use this header to specify the encryption algorithm. The header value must be "AES256".
x-amz-server-side​-encryption​-customer-key Use this header to provide the 256-bit, base64-encoded encryption key for Amazon S3 to use to encrypt or decrypt your data.
x-amz-server-side​-encryption​-customer-key-MD5 Use this header to provide the base64-encoded 128-bit MD5 digest of the encryption key according to RFC 1321. Amazon S3 uses this header for a message integrity check to ensure the encryption key was transmitted without error.
If you use the Amazon Java SDK, doing this is easy and examples are provided in their documentation. But to do so using JetS3t, you can do the following:
Assuming s3Object is the object you are trying to put on S3, call the following for each of the above mentioned headers with appropriate values.
s3Object.addMetadata("<header>", "<header_value>")

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