@dkocher commented

When transferring files to some services (Backblaze B2, Amazon S3), a checksum is provided with the file data sent to allow the server to check the integrity. For WebDAV, OpenStack Swift uploads we also check the integrity of the file by calculating a checksum and comparing it with the response from the server after the upload completes. For FTP and SFTP no integrity check is performed.

Duplicate for #9367.

f9bca12 commented

Do I understand correctly - for Amazon S3, the checksum verification is performed automatically such that all files uploaded with Cyberduck have file integrity verified and we do not need to perform any other integrity checks on these files?

@dkocher commented

Replying to [comment:4 DvdinSD]:

Do I understand correctly - for Amazon S3, the checksum verification is performed automatically such that all files uploaded with Cyberduck have file integrity verified and we do not need to perform any other integrity checks on these files?

That is true. For Amazon S3, files are verified both by AWS when the file is received and compared with the checksum sent by Cyberduck. Additionally we also compare the checksum returned by AWS for the uploaded file with the checksum computed locally.

@dkocher commented

If the checksums do not match you will get an error Mismatch between {0} hash {1} of downloaded data and ETag {2} returned by the server for downloads and Mismatch between MD5 hash {0} of uploaded data and ETag {1} returned by the server for uploads .