peass-ng/PEASS-ng · error · InvalidOperationException

AES engine not initialised

Error message

AES engine not initialised

What it means

ProcessBlock throws this InvalidOperationException when WorkingKey is null, i.e. EncryptBlock/DecryptBlock is attempted before Init was called successfully. AES requires the key schedule before any block can be processed.

Solutions

1. Call engine.Init(forEncryption, new KeyParameter(key)) before ProcessBlock
2. Verify the earlier Init did not throw (it leaves WorkingKey null)
3. Re-create or re-Init the engine after any failure

Example fix

// before
var engine = new AesEngine();
engine.ProcessBlock(input, 0, output, 0);
// after
var engine = new AesEngine();
engine.Init(true, new KeyParameter(key));
engine.ProcessBlock(input, 0, output, 0);

if (!initialized) cipher.Init(forEncryption, new KeyParameter(key));

static bool IsAesReady(AesEngine e) => e != null; // WorkingKey is private; track init yourself

try { cipher.ProcessBlock(input, 0, output, 0); } catch (InvalidOperationException ex) { /* lazy-Init then retry */ }

When it happens

Trigger: Calling ProcessBlock on a new AesEngine without Init, after Init threw (e.g. bad key length), or after the engine was reset without re-initializing.

Common situations: Deferred initialization logic that skips Init, an earlier Init exception swallowed by logging code, or sharing an engine instance across threads before it's initialized.

Related errors

• Gost28147 engine not initialised
• invalid parameter passed to AES init -
• Key length not 128/192/256 bits.
• Should never get here
• Skein engine is not initialised.

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/126d7482ecef87bb. Report an issue: GitHub.

Appendix: source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/crypto/engines/AesEngine.cs:486

        public virtual bool IsPartialBlockOkay
        {
            get { return false; }
        }

        public virtual int GetBlockSize()
        {
            return BLOCK_SIZE;
        }

        public virtual int ProcessBlock(
            byte[] input,
            int inOff,
            byte[] output,
            int outOff)
        {
            if (WorkingKey == null)
                throw new InvalidOperationException("AES engine not initialised");

            Check.DataLength(input, inOff, 16, "input buffer too short");
            Check.OutputLength(output, outOff, 16, "output buffer too short");

            UnPackBlock(input, inOff);

            if (forEncryption)
            {
                EncryptBlock(WorkingKey);
            }
            else
            {
                DecryptBlock(WorkingKey);
            }

            PackBlock(output, outOff);

            return BLOCK_SIZE;

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