Summary: As a trainee, I got the task to extract encrypted passwords of our external password manager (Zoho Vault) and decrypt them. The documentation regarding how to decrpyt them is...none. I ask the support for help, but they send me only some pages of their documentation...

Research and attempts: According of my account and the documentation of Zoho Vault API, the algorithm is a "PBKDF2_AES". I used at first the PBKDF2 encryption to generate a key, by using a passphrase + a salt + an iteration of 1000, which I received with some API calls. Next, I tried to use the Zoho Vault decrypting function (which decrypts AES encryptions), but I didnt got the result I wanted. After that, I checked an Online AES Encrypter/Decrypter and tried my luck there. After filling the forms with all the required info, I received an error. Just to be sure, that it was the right encrypt/decrypt method, I encrypted some other example data and the result had the same Base64 pattern password I tried to encrypt. After I checked the "PBKDF2 generated key" and mine. The one I made was for a AES-256. But the "PBKDF2 generated key" seems to be 64 byte long/AES-512.

Which I did some research and it almost seems it doesnt exist.

I just cant figure out how to continue... If needed, I can share all required keys and encrypted data, since they are all dummies for the later used account anyway.

  • 2
    $\begingroup$ "it almost seems it doesnt exist"; AES-512 doesn't exist. Actually, there are a few proposals for "augmented AES" out there, however they aren't AES, no one takes them seriously, and (AFAIK) aren't used anywhere in practice... $\endgroup$
    – poncho
    Commented Aug 27, 2020 at 15:25
  • 1
    $\begingroup$ Also: standard password hashing (as strongly suggested by PBKDF2) is normally not actual encryption: there is no computationally efficient way to find the password from the password hash, even with knowledge of the key/pepper (if any). If there's a better way than checking a password guess, the system is considered broken. Have you been sent on a snipe hunt? $\endgroup$
    – fgrieu
    Commented Aug 27, 2020 at 19:25

1 Answer 1


But the "PBKDF2 generated key" seems to be 64 byte long

Sounds like the algorithm is actually PBKDF2-SHA512 or some other 512-bit has function, as PBKDF2 does NOT use AES as its PRF. Generally this is truncated down to 256 bits to use with your block cipher. I would check what you are using as the PRF, try replicating the master key by choosing different 512-bit hash functions until you get a match, then work onto decryption after.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.