What causes "Failed to get crypto " in MuntashirAkon/AppManager?

Verify the BackupItem's crypto settings (keystore path, key alias, passwords, cipher mode) are valid before calling convert().

MuntashirAkon/AppManager · error · BackupException

Failed to get crypto

Error message

Failed to get crypto

What it means

TBConverter.convert() wraps CryptoException from ConvertUtils.getV5Metadata() (which computes the destination crypto/keystore parameters for the converted backup) into a BackupException. It means the metadata conversion could not obtain the cryptographic settings (key alias, cipher, keystore access) needed to build the v5 destination metadata.

Solutions

Verify the BackupItem's crypto settings (keystore path, key alias, passwords, cipher mode) are valid before calling convert().
Re-create or re-select the encryption key/keystore, or set the backup to unencrypted if crypto is not needed.
Inspect the wrapped CryptoException cause for the underlying keystore/algorithm error and fix it accordingly.

Example fix

// before
mBackupItem.setCryptoAlgo(CryptoUtils.CRYPTO_AES_GCM); // with missing/invalid keystore
convert();
// after
if (CryptoUtils.getKeystore().isPresent()) {
    mBackupItem.setCryptoAlgo(CryptoUtils.CRYPTO_AES_GCM);
    convert();
} else {
    throw new IllegalStateException("Select or create a keystore key before converting to encrypted backup");
}

Defensive patterns

Strategy: validation

Validate before calling

// Kotlin/Java pseudo-check before convert()
if (mBackupItem.isEncrypted()) {
    if (!CryptoUtils.hasValidKey(mDestMetadata.crypto.keyAlias)) {
        throw new IllegalStateException("Configure a valid keystore key before converting to encrypted backup");
    }
}

Type guard

fun CryptoInfo?.isValid(): Boolean = this != null && !keyAlias.isNullOrBlank() && algo != null

Try / catch

try {
    converter.convert();
} catch (BackupException e) {
    if (e.getCause() instanceof CryptoException ce) {
        Log.e(TAG, "Crypto setup failed: " + ce.getMessage());
        promptUserToSelectKey();
    }
}

Prevention

Always initialize/select the keystore key before running any conversion to a crypto destination format.
Test keystore access (load + alias existence) at app startup when encrypted backups are enabled.
Keep keystore passwords in secure storage and verify the alias exists before conversion.

When it happens

Trigger: Calling convert() on a source backup whose destination metadata requires crypto info that cannot be resolved: ConvertUtils.getV5Metadata(mSourceMetadata, mBackupItem) throws CryptoException because the destination backup item's crypto settings (keystore/key/algorithm) are unavailable or invalid.

Common situations: Converting a backup to the encrypted (TAR+GZIP+CRYPTO) format without a valid keystore or a key selected; keystore file missing/corrupted; a keystore password or key alias mismatch; the destination metadata references a crypto mode unsupported by the configured encryption algorithm.

Related errors

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/f428c4f445b0a240. Report an issue: GitHub.

Appendix: source

Thrown at app/src/main/java/io/github/muntashirakon/AppManager/backup/convert/TBConverter.java:124

            throw new BackupException("Could not read package name.");
        }
        // Source metadata
        mSourceMetadata = readPropFile();
        // Simulate a backup creation
        try {
            mBackupItem = BackupItems.createBackupItemGracefully(mUserId, "TB", mPackageName);
        } catch (IOException e) {
            throw new BackupException("Could not get backup files", e);
        }
        boolean backupSuccess = false;
        try {
            try {
                // Destination metadata
                mDestMetadata = ConvertUtils.getV5Metadata(mSourceMetadata, mBackupItem);
                // Destination APK will be renamed
                mDestMetadata.metadata.apkName = "base.apk";
            } catch (CryptoException e) {
                throw new BackupException("Failed to get crypto " + mDestMetadata.info.crypto, e);
            }
            try {
                mChecksum = mBackupItem.getChecksum();
            } catch (IOException e) {
                throw new BackupException("Failed to create checksum file.", e);
            }
            // Backup icon
            backupIcon();
            if (mDestMetadata.info.flags.backupApkFiles()) {
                backupApkFile();
            }
            if (mDestMetadata.info.flags.backupData()) {
                backupData();
            }
            // Write modified metadata
            try {
                Map<String, String> filenameChecksumMap = MetadataManager.writeMetadata(mDestMetadata, mBackupItem);
                for (Map.Entry<String, String> filenameChecksumPair : filenameChecksumMap.entrySet()) {

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