7z technical7z AES-256 Key Derivation
7z derives encryption material from the password, a salt, and parameters encoded in the archive. The design deliberately makes each candidate expensive, so archive-specific settings and password clues matter more than one published speed number.
The parameters live in the archive
A 7z encoded header carries what a compatible decoder needs to derive keys and initialise AES. The iteration or cycle setting is not a universal constant across every archive, so a tool should read it rather than assume a fixed value.
When headers are encrypted, even the file list is protected by the same password-derived material. That is why a utility can appear unable to list files while still handling a perfectly healthy archive.
Cipher
AES-256
Inputs
Password + salt + parameters
Cost
Archive-specific
Metadata
Headers may be hidden
What this means for recovery
A candidate verifier can test a focused dictionary or mask, but the candidate space has to come from real evidence. A random long password remains impractical whether the hardware is local or remote.
If a candidate seems to work, extract several files and check their integrity. A listing, or one successful entry, does not rule out damage elsewhere in a solid archive.
Avoid universal benchmark claims
Throughput depends on the archive parameters, the implementation, the GPU, the thermal state and the verification mode. Report a measured sample with its conditions, or describe the factors qualitatively; do not present one number as a promise for every 7z file.
Use the archive's own parameters
A technical page is useful when it improves diagnosis. Hardcoded iteration counts and success percentages can send a user down the wrong path.
Frequently asked questions
Does every 7z file use the same number of iterations?
Does AES-256 make a 7z password impossible to recover?
Why does a benchmark differ between two 7z files?
Need a second opinion on this file?
Run the free local check first. If the file is healthy and you are authorized to recover it, you can compare the evidence with a specialist's supported workflow.
Related guides
For authorized owner use only. Recovery depends on the exact file and password; no outcome is guaranteed. FilesUnlock is a separate product from the recovery service that processes submissions.