I have a text file in which I store all my bank details. I compress and encrypt it with 7-Zip using the following parameters:
- Archive format: 7z
- Compression level: Ultra
- Compression method: LZMA2
- Dictionary size: 64 MB
- Solid Block size: 4 GB
- Number of CPU threads: 4
- Encryption method: AES-256
- Encrypt file names: True
The password for the encryption is chosen such that it won't be found in any dictionary and is rather an almost random string (composed of 15-20 upper and lower case letters, numbers, and symbols). I do not store this password anywhere.
Also, the filename of the text file is kept such that no one will be able to tell that the file is related to bank details at all.
Is this secure enough, under the following scenarios?
- The attacker takes full control of the system, but does not know that this particular file is of any importance to him.
- The attacker is in possession of the file, and is actively trying to decrypt it, knowing that it has the bank details.