Between Silk and Cyanide (73 page)

'Do you believe they're breakable on a depth of two?'

I dropped my unlit cigar. I couldn't believe that an expert cryptographer was asking me a question which a FANY coder could have answered without the slightest difficulty.

'Take your time.'

'I'm certain they can be. I've done it myself with the help of the FANYs.'

He immediately asked for details, and I became more convinced than ever that I was on some kind of trial.

Still wondering what the hell I'd done wrong apart from being born, I said that despite our warnings that used code-groups must be destroyed at once, agents often used the same ones twice; in order to see how much damage a 'depth of two' caused I'd asked a supervisor to encipher two messages on the same code-groups without telling anyone the texts (which were scabrous), and after feeling our way for twenty-four hours the girls and I had cracked them.

'How?'

What's he expecting—a cryptographic breakthrough?

'Nothing new, sir. I used the system I'd been taught at Bedford but adapted it a bit.' I showed him the adaptation which I'd passed on to the girls, and wondered why he spent so long studying it.

'Has anyone else seen this, apart from you and the coders?'

'No, sir.'

Good God, he can sigh.

'… perhaps there's something else I should mention, sir.'

'I've little doubt of it.'

I added that although one-time pads were simple enough to be agent-proof, they'd found so many ways to send indecipherables in them that I'd given the girls nine guidelines on the quickest way to break them.

He studied them in silence, then asked if I'd sent a copy to Tiltman. He didn't wait for my answer. 'Why not?'

'They're so elementary by Bletchley's standards.'

'I see. I suggest you send them copies of the guidelines and the "adaptation", if possible today. I'd also like copies myself.'

I made a note to dispatch them because I knew I'd want to forget it.

'… it's Denniston with two 'n's… Nick will know where to send them.'

I looked up to find him studying me intently.

I've been sucked into the inner space of an uncluttered mind.

'I doubt if you confine your deception schemes to WOKs and dummy traffic… Do you ever Gift-horse one-time pads?'

Is the bastard telepathic?

'I'm working on a way to do it, but it's still only an itch. I'll be scratching it tonight.'

He asked me to tell him the principle (a word seldom used in SOE).

'It's to make one-time messages look as if they've been enciphered on the same code-groups… it could waste a lot of the Boche's time if they fall for it.'

'Keep scratching… Which brings me to my next point. I understand you've devised a mental one-time pad.'

Is there anything Nick hasn't told him?

'How's the system work?'

It usually took me an hour to explain the complexities of a MOP, but he nod-nodded his way through them in under five minutes, and had only one question. 'Have you shown this code to Bletchley?'

To which I had only one answer—'No. I thought it was secure enough not to need vetting.'

'Of course it bloody well is, but that's not the point…' Controlling his anger (but only just) Commander Two Us abruptly changed the subject. 'A year or so ago you showed Tiltman some charts you'd devised for breaking indecipherables '

Forestalling him, I said that I'd sent the charts to Bletchley.

'But surely you've amended them since then?'

'Well… here and there.'

'What's your current breaking-rate?'

'Ninety per cent in under six hours.'

'Send the amendments to Bletchley.'

He waited impatiently while I made a note, then jerked his finger at the FFI code-book. 'How long after you'd broken the secret French code in front of them did you deliver that code-book to Algiers?' I was no longer surprised by anything he knew or asked. 'Five or six weeks.'

His next comment was more to himself than to me: 'That codebook's clearly intended for de Gaulle's provisional government.'

Is that why he studied the vocabulary so carefully?

'Do you supply code-books to any governments-in-exile?'

'We supply them to their agents, but I doubt if the vocabularies would be much use to their governments…'

Wondering if this were a clue to his job, and wishing he'd go back to it, I suddenly remembered the Bardsea episode. 'We had to send two hundred one-time pads to the Poles for an unspecified purpose.'

'Ah.'

It was then that I saw a new Commander Two Us. Glancing at his watch as if it had been Gift-horsed, he said with a hint of shyness that he'd be glad of some coffee if the offer were still open.

'Absolutely.'

I pressed the buzzer twice, and a few moments later the sight of Muriel carrying in her tray had its customary effect, even on him. He accepted the coffee gratefully but declined the sandwiches as he'd arranged to have lunch with Nick. But despite his friendliness, something warned me that he was about to make a meal of me.

I hadn't long to wait. 'It's time I spoke to you frankly…'

I noticed how bright his eyes were, though they could no longer conceal how long they'd been open.

'You have great responsibilities, and you don't need me to tell you that you've done a damn good job—you started off with poem-codes and ended with all this…' He glanced at the silks but seconds later his tone stopped matching them.

'It's not your ability I'm questioning, it's your attitude…' He leaned forward until we were only a few miles apart. 'Don't you realize that Bletchley has to deal with all grades of cipher, and needs every bit of help it can get? Hasn't it occurred to you that some of your unorthodoxies would interest them greatly—Gift-horse and MOPs to name only two? But what chance do you give them to judge for themselves? You wait for people like Dudley-Smith to visit you a couple of times a year, and then show them the minimum. Why must you be so damn insular? You don't strike me as being modest, but surely you're aware that your approach to codes is, to say the least, uncommon, and could be of the utmost value to Bletchley and others. I urge you from this moment onwards to pass on new ideas like Gift-horsing one-time pads because SOE isn't the only organization trying to kick the Boche in their cryptographic balls… and now, if I may, I'll try one of those sandwiches.'

He tried two but I didn't join him because I knew that he hadn't quite finished with me.

'John tells me that you've still not visited Bletchley.'

'No, sir.'

'Why not?'

'I might want to stay there.'

'They might even let you'—his eyes twinkled—'if only because you're the one that got away.' He looked slowly round the office.

'Perhaps it's as well that you did.'

He stood up and held out his hand, which was a lot drier than mine. 'You've been more help to me than you can possibly know.' He closed the door quietly.

I still didn't know what he did or why he'd come.

There's a club among senior signals officers and I'll never be admitted to it, and aspects of the code war I'll never understand.
[42]

Ten minutes later I began Gift-horsing LOPs.

During the past two months, which felt more like centuries, SHAEF had made radical changes to SOE's structure, many of them long overdue.

On 1 May they'd ordained that SOE in London should henceforth be known as Special Forces Headquarters, and that our OSS counterparts should cease calling themselves 0/S and adopt the same cover.

In mid-June they insisted on amalgamating our rival French sections, and gave Buckmaster and Passy an outer limit of 1 July in which to place themselves and their resources under the command of General Koenig, head of the EMFII (Etat-Majeur des Forces Françaises de 1'Interior), which had been created for the sole purpose of controlling all Resistance groups which had previously worked for either French section.

SHAEF then implemented a decision which stood the Signals directorate on what remained of its head. They established an SFHQ in France. It was known as Special Forces Advanced Headquarters, and was adjacent to their own Advanced Headquarters. By mid-June it was already in operation and by July many of SOE's finest (including Robin Brook) had left Baker Street to advise SHAEF on what the Resistance could deliver.

There were no communication problems as all messages between Brook and Co. and London were exchanged in one-time pads, but at the beginning of July Special Forces Advanced (though in Signals matters retarded) HQ informed Nick that it was essential for them to be able to exchange messages at short notice with circuits of agents anywhere in France. They also informed him that this same facility was required by SOE's representatives with 21 Army Group and the 1st British and 2nd Canadian armies.

But even that wasn't all. Army commanders needed to order agents anywhere in France to sabotage specific targets at short notice. It was taken for granted that SOE's Signals directorate would provide the solution forthwith.

It took six of us twelve agonizing hours to devise a three-way communication system, though we couldn't be sure it would work.

A week later it was fully operational. All messages for agents were relayed to London by SFHQ, and we then re-enciphered them in the agents' own codes and retransmitted them. Conversely, agents sent their replies to London in WOKs or LOPs and we re-enciphered them in one-time pads, and re-transmitted them to SFHQ. With Nick's backing I'd refused to allow any of the three-way traffic to be retransmitted in the poem-codes which still bedevilled segments of our traffic.

The urgency of the messages was unlike any we'd known, and the code rooms in London and our three WT stations had to pool their resources to minimize delay.

But by 1 July the satisfaction of watching the girls achieve impossible targets was put into perspective by one of the most sickening telegrams ever to pass through the code room.

It was transmitted by Roger (Francis Cammaerts), who'd been appointed head of all Allied missions in south-eastern France, and who'd organized Jockey, a railway-demolition network in the AlpesMaritimes, which was on a par with Pimento. Cammaerts had repeatedly warned London that without the heavy weapons which the Americans had promised to drop, the freedom fighters at Vercors would have no chance of withstanding a major German counterattack, and he was convinced that they'd be wiped out if they didn't disperse immediately.

A week later the Germans landed crack SS troops on the Vercors plateau, and overwhelmed the lightly armed Maquis. In the carnage which followed one woman was raped by seventeen men in succession while a German doctor held her pulse, ready to restrain the soldiers if she fainted. Another woman was disembowelled, and left to die with her intestines wound round her neck. A third had the fingers of both hands amputated.

It was no consolation to the girl who decoded the message to learn from subsequent messages that the Americans had broken through in Brittany, that the SAS and the Resistance had secured the Breton countryside, and that the Jedburghs had finally (and successfully) gone into action. She asked to be transferred to other duties, and I put her to work Gift-horsing WOKs.

I escaped from Vercors by spending the next eight hours attacking our first indecipherable from a Jedburgh. It had been transmitted by Andy in his one-time pad, and had already defied three blanket attacks and my so-called guidelines.

Eleven hundred failures later I threw the pad on to the floor in disgust, and discovered that instead of starting on page one of his pad he'd started on page six, a major cryptographic breakthrough. (I subsequently learned that he'd detached page six so that he could always have a sheet of his pad with him, and had decided to use it before it became too crumpled.)

His message made disturbing reading, if anything could be after Vercors. Two members of his team had met with accidents on landing and had broken three legs between them.

Eleven other Jedburgh teams were also operating in France, and their encoding was flawless. (One message stated, 'We're now sitting and waiting', which puzzled the Jedburgh section but which I took to be a reference to our Milton Hall encounter.)

No longer quite so 'damn insular', thanks to Commander Two Us, I noticed that the attempt to merge our rival French sections under Koenig had only driven them further apart, whereas the fusion of SOE and a branch of the OSS into SFHQ had had the opposite effect.

The Americans were more co-operative than ever, and had supplied us with large quantities of silk, which we badly needed to produce new codes for the Middle East and Burma. Their eagerness to help in every way they could may have been due to the difficulties we suspected them of having with Sussex (their Intelligence-gathering operation with C), though they never referred to them. And under the leadership of Captain Phoenix their code room at Station 53c had quickly mastered the complex re-encipherment drill, and had developed a character of its own, as any good code-room should.

I became totally absorbed in trying to speed up the three-way system, and was surprised when Nick ordered me to report to his office immediately. I was sitting rigidly at his desk with Heffer only a puff or two away. Whatever they'd been discussing had drained the room of air.

'What I have to tell you is highly confidential.' With a quick glance at Heffer, he extracted three documents from a Top Secret folder.

'These mustn't be discussed outside this room…'

He seemed uncertain how to proceed or even whether he should, but finally said that three messages in code had been intercepted and the only thing he could tell me about them was that I had to break them as quickly as possible. 'The last message is incomplete,' he added.

So was his summary. He'd said nothing about who'd sent the messages, who'd intercepted them, or why they were in his possession, and Heffer's expression warned me not to ask.

I was finally allowed to look at them. 'It's obviously a substitute code of some kind—any idea what language they're in?'