What causes "Could not get crypto " in MuntashirAkon/AppManager?

Supply the correct password/key used when the backup was created

MuntashirAkon/AppManager · error · BackupException

Could not get crypto

Error message

Could not get crypto

What it means

After availability checks pass, RestoreOp calls mBackupItem.setCrypto(mBackupInfo.getCrypto()); a CryptoException is wrapped as BackupException 'Could not get crypto <mode>'. Unlike error 100 this happens on the restore path and the backup item is cleaned up before aborting.

Source

Thrown at app/src/main/java/io/github/muntashirakon/AppManager/backup/RestoreOp.java:128

        mBackupItem = backupItem;
        mUserId = userId;
        try {
            mBackupInfo = mBackupItem.getInfo();
            mBackupFlags = mBackupInfo.flags;
        } catch (IOException e) {
            mBackupItem.cleanup();
            throw new BackupException("Could not read backup info. Possibly due to a malformed json file.", e);
        }
        // Setup crypto
        if (!CryptoUtils.isAvailable(mBackupInfo.crypto)) {
            mBackupItem.cleanup();
            throw new BackupException("Mode " + mBackupInfo.crypto + " is currently unavailable.");
        }
        try {
            mBackupItem.setCrypto(mBackupInfo.getCrypto());
        } catch (CryptoException e) {
            mBackupItem.cleanup();
            throw new BackupException("Could not get crypto " + mBackupInfo.crypto, e);
        }
        try {
            mBackupMetadata = mBackupItem.getMetadata(mBackupInfo).metadata;
        } catch (IOException e) {
            mBackupItem.cleanup();
            throw new BackupException("Could not read backup metadata. Possibly due to a malformed json file.", e);
        }
        // Get checksums
        try {
            mChecksum = mBackupItem.getChecksum();
        } catch (Throwable e) {
            mBackupItem.cleanup();
            throw new BackupException("Failed to get checksums.", e);
        }
        // Verify metadata
        if (!requestedFlags.skipSignatureCheck()) {
            try {
                verifyMetadata();

View on GitHub (pinned to 0152f468fc)

Solutions

Supply the correct password/key used when the backup was created
Ensure all crypto key files/directories belonging to the backup were copied together with the backup
Inspect the wrapped CryptoException cause to distinguish wrong-key from missing-backend problems
Re-create the backup with a working crypto mode if key material is unrecoverable

Example fix

// before
try {
    mBackupItem.setCrypto(mBackupInfo.getCrypto());
} catch (CryptoException e) {
    mBackupItem.cleanup();
    throw new BackupException("Could not get crypto " + mBackupInfo.crypto, e);
}
// after
try {
    mBackupItem.setCrypto(mBackupInfo.getCrypto());
} catch (CryptoException e) {
    mBackupItem.cleanup();
    throw new BackupException("Could not get crypto " + mBackupInfo.crypto
            + ": check password/key availability (cause: " + e.getMessage() + ")", e);
}

Defensive patterns

Strategy: try-catch

Validate before calling

// after isAvailable passes, verify key material exists for the mode before setCrypto
if (!CryptoUtils.hasKeyMaterial(backupDir, mode)) throw new BackupException("Key/password for mode " + mode + " not available");

Try / catch

try { new RestoreOp(...); } catch (BackupException e) { if (e.getMessage().startsWith("Could not get crypto")) { promptForPassword(); } throw e; }

Prevention

Store the backup password in a password manager at backup time
Copy crypto key files together with the rest of the backup
Note the crypto mode used so you can reinstall its provider on new devices

When it happens

Trigger: setCrypto initialization fails despite isAvailable passing: wrong password/key derivation failure, corrupted key files, or the crypto backend throwing during setup for the encrypted backup.

Common situations: User restored a backup without its paired key/password; encrypted backup transferred without the hidden key directory; ROM update changed key storage semantics.

Related errors

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/284eae9ca9d59303. Report an issue: GitHub.