is a two-way street. You can Encrypt
and then you can Decrypt
Encryption provides Confidentiality of the Message but provides no Integrity of the Message.
Hashing, well at least Secure Hash Algorithms, is a one-way street. You can Hash the Message but you can not un-Hash the Message.
Hashing provides Integrity of a Message but provides no Confidentiality.
When you require Confidentiality and Integrity, you must use both Encryption and Hashing.
If you need Non-Repudiation, then you need to TODO
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