What is attestation for Confidential Computing?

Without attestation, you’re not really doing Confidential Computing.

This post – or the title of this post – has been sitting in my “draft” pile for about two years. I don’t know how this happened, because I’ve been writing about Confidential Computing for three years or so years by now, and attestation is arguably the most important part of the entire subject.

I know I’ve mentioned attestation in passing multiple times, but this article is devoted entirely to it. If you’re interested in Confidential Computing, then you must be interested in attestation, because, without it, you’re not doing Confidential Computing right. Specifically, without attestation, any assurances you may think you have about Confidential Computing are worthless.

Let’s remind ourselves what Confidential Computing is: it’s the protection of applications and data in use by a hardware-based TEE (Trusted Execution Environment). The key benefit that this brings you is isolation from the host running your workload: you can run applications in the public cloud, on premises or in the Edge, and have cryptographic assurances that no one with access to the host system – hypervisor access, kernel access, admin access, even standard hardware access[1] – can tamper with your application. This, specifically, is Type 3 – workload from host – isolation (see my article Isolationism – not a 4 letter word (in the cloud) for more details), and is provided by TEEs such as AMD’s SEV and Intel’s SGX – though not, crucially, by AWS Nitro, which does not provide Confidential Computing capabilities as defined by the Confidential Computing Consortium.

Without attestation, you’re not really doing Confidential Computing. Let’s consider a scenario where you want to deploy an application using Confidential Computing on a public cloud. You ask your CSP (Cloud Service Provider) to deploy it. The CSP does so. Great – your application is now protected: or is it? Well, you have no way to tell, because your CSP could just have taken your application, deployed it in the normal way, and told you that it had deployed it using a TEE. What you need is to take advantage of a capability that TEE chips provide called an attestation measurement to check that a TEE instance was actually launched and that your application was deployed into it. You (or your application) asks the TEE-enabled chip to perform a cryptographically signed measurement of the TEE set-up (which is basically a set of encrypted memory pages). It does so, and that measurement can then be checked to ensure that it has been correctly set up: there’s a way to judge whether you’re actually doing Confidential Computing.

So, who does that checking? Doing a proper cryptographic check of an attestation measurement – the attestation itself – is surprisingly[2] tricky, and, unless you’re an expert in TEEs and Confidential Computing (and one of the points of Confidential Computing is to make is easy for anyone to use these capabilities), then you probably don’t want to be doing it.

Who can perform the validation? Well, one option might be for the validation to be done on the host machine that’s running the TEE. But wait a moment – that makes no sense! You’re trying to isolate yourself from that machine and anyone who has access to it: that’s the whole point of Confidential Computing. You need a remote attestation service – a service running on a different machine which can be trusted to validate the attestation and either halt execution if it fails, or let you know so that you can halt execution.

So who can run that remote attestation service? The obvious – obvious but very, very wrong – answer is the CSP who’s running your workload. Obvious because, well, they presumably run Confidential Computing workloads for lots of people, but wrong because your CSP is part of your threat model. What does this mean? Well, we talked before about “trying to isolate yourself from that machine and anyone who has access to it”, the anyone who has access to it is exactly your CSP. If the reason to be using Confidential Computing is to be able to put workloads in the public cloud even when you can’t fully trust your CSP (for regulatory reasons, for auditing reasons, or just because you need higher levels of assurance than existing cloud computing), then you can’t trust your CSP to provide the remote attestation service. To be entirely clear: if you allow your CSP to do your attestation, you lose the benefits of Confidential Computing.

Attestation – remote attestation – is vital, but if we can’t trust the host or the CSP to do it, what are your options? Well, either you need to do the attestation yourself (which I already noted is surprisingly difficult), or you’re going to need to find a third party to do that. I’ll be discussing the options for this in a future article – keep an eye out.

1 – the TEEs used for Confidential Computing don’t aim to protect against long-term access to the CPU by a skilled malicious actor – but this isn’t a use case that’s relevant to most users.

2 – actually, not that surprising if you’ve done much work with cryptography, cryptographic libraries, system-level programming or interacted with any silicon vendor documentation.

My book at RSA Conference NA

Attend RSA and get 20% off my book!

Attend RSA and get 20% off my book!

I’m immensely proud (as you can probably tell from the photo) to be able to say that my book in available in the book store at the RSA Conference in San Francisco this week. You’ll find the store in Moscone South, up the escalators on the Esplanade.

If you ever needed a reason to attend RSA, this is clearly the one, particularly with the 20% discount. If anyone’s interested in getting a copy signed, please contact me via LinkedIn – I currently expect to be around till Friday morning. It would be great to meet you.

Trust book – playlist!

A playlist of music to which I’d listened and which I’d enjoyed over the months it took to write the book.

I had probably more fun than I deserved to have writing the acknowledgements section of my book, Trust in Computer Systems and the Cloud (published by Wiley at the end of December 2021). There was another section which I decided to add to the book purely for fun: a playlist of music to which I’d listened and which I’d enjoyed over the months it took to write. I listen to a lot of music, and the list is very far from a complete one, but it does represent a fair cross-section of my general listening tastes. Here’s the list, with a few words about each one.

One thing that’s missing is any of the classical music that I listen to. I decided against including this, as I’d rarely choose single tracks, but adding full albums seemed to miss the point. I do listen to lots of classical music, in particular sacred choral and organ music – happy to let people have some suggestions if they’d like.

  • Secret Messages – ELO – I just had to have something related (or that could be considered to be related) to cryptography and security. This song isn’t, really, but it’s a good song, and I like it.
  • Bleed to Love Her – Fleetwood Mac – Choosing just one Fleetwood Mac song was a challenge, but I settled on this one. I particularly like the harmonics in the version recorded live at Warner Brothers Studio in Burbank.
  • Alone in Kyoto – Air – This is a song that I put on when I want to relax. Chiiiiilllll.
  • She’s So Lovely – Scouting for Girls – Canonically, this song is known as “She’s A Lovely” in our family, as that’s what we discovered our daughters singing along to when we played it in the car many years ago.
  • Prime – Shearwater – This is much more of an “up” song when I want to get an edge on. Shearwater have a broad range of output, but this is particular favourite.
  • Stay – Gabrielle Aplin – I like the way this song flips expectations on its head. A great song by a talented artist.
  • The Way I Feel – Keane – A song about mental health.
  • Come On, Dreamer – Tom Adams – Adams has an amazing voice, and this is a haunting song about hope.
  • Congregation – Low – I discovered this song watching DEVS on Amazon Prime (it was originally on Hulu). Low write (and perform) some astonishing songs, and it’s really worth going through their discography if you like this one.
  • Go! – Public Service Broadcasting – You either love this or hate it, but I’m in the “love” camp. It takes original audio from the Apollo 11 moon landing and puts it to energising, exciting music.
  • The Son of Flynn (From “TRON: Legacy”/Score) – Daft Punk – TRON:Legacy may not be not the best film ever released, but the soundtrack from Daft Punk is outstanding Electronica.
  • Lilo – The Japanese House – A song about loss? About hope? Another one to chill to (and tha band are great live, too).
  • Scooby Snacks – Fun Lovin’ Criminals – Warning: explicit lyrics (from the very beginning!) A ridiculous song which makes me smile every time I listen to it.
  • My Own Worth Enemy – Stereophonics – I slightly surprised myself by choosing this song from the Stereophonics, as I love so many of their songs, but it really does represent much of what I love about their oeuvre.
  • All Night – Parov Stelar – If you ever needed a song to dance to as if nobody’s watching, this is the one.
  • Long Tall Sally (The Thing) – Little Richard – Sometimes you need some classic Rock ‘n’ Roll in your life, and who better to provide it?
  • Shart Dressed Man – ZZ Top – “Black tie…” An all-time classic by men with beards. Mostly.
  • Dueling Banjos – Eric Weissberg – I first heard this song at university. It still calls out to me. There are some good versions out there, but original from the songtrack to Deliverance is the canonical one. And what a film.
  • The Starship Avalon (Main Title) – Thomas Newman – This (with some of the others above) is on a playlist I have called “Architecting”, designed to get me in the zone. Another great film.
  • A Change is Gonna Come – Sam Cooke – A song of sadness, pain and hope.
  • This Place – Jamie Webster – A song about Liverpool, and a family favourite. Listen and enjoy (the accent and the song!).

If you’d like to listen to these tracks yourself, I’ve made playlists on my two preferred audio streaming sites: I hope you enjoy.

Spotify – Trust in Computer Systems and the Cloud – Bursell

Qobuz – Trust in Computer Systems and the Cloud – Bursell

As always, I love to get feedback from readers – do let me know what you think, or suggest other tracks or artists I or other readers might appreciate.

“Trust in Computer Systems and the Cloud” published

I’ll probably have a glass or two of something tonight.

It’s official: my book is now published and available in the US! What’s more, my author copies have arrived, so I’ve actually got physical copies that I can hold in my hand.

You can buy the book at Wiley’s site here, and pre-order with Amazon (the US site lists is as “currently unavailable”, and the UK site lists is as available from 22nd Feb, 2022. ,though hopefully it’ll be a little earlier than that). Other bookstores are also stocking it.

I’m over the moon: it’s been a long slog, and I’d like to acknowledge not only those I mentioned in last week’s post (Who gets acknowledged?), but everybody else. Particularly, at this point, everyone at Wiley, calling out specifically Jim Minatel, my commissioning editor. I’m currently basking in the glow of something completed before getting back to my actual job, as CEO of Profian. I’ll probably have a glass or two of something tonight. In the meantime, here’s a quote from Bruce Schneier to get you thinking about reading the book.

Trust is a complex and important concept in network security. Bursell neatly unpacks it in this detailed and readable book.

Bruce Schneier, author of Liars and Outliers: Enabling the Trust that Society Needs to Thrive

At least you know what to buy your techy friends for Christmas!

Book delay

(You can still win a free copy)

I’m sorry to have to announce that the availability of my book, Trust in Computrer Systems and the Cloud, is likely to be delayed. Wiley, my publisher, had hoped to get copies in the US for early December, and to Europe a month or so after that, but problems getting hold of paper (a core component of physical books, for the uninitiated) mean that these dates will be delayed.

I’m obviously disappointed about this, but it’s really not Wiley’s fault (the paper shortage is wide-spread across the US, it appears). Travel rules permitting, I intend to attend the RSA Conference in San Francisco in February 2022, and we hope to have copies of the book available there (book your signed copy now[1]).

Anyway, sorry to announce this, but it does give you more time to follow this blog, giving you a chance of a free copy when they are available.

1 – I will, actually, sign[2] your copy if you like: do feel free to contact me!

2 – I’m hoping we don’t get to the stage where, as in the film[3] Notting Hill, unsigned copies are worth more than signed ones!

3 – yeah, yeah, “movie” if you must.

Image by Peggychoucair from Pixabay

Cloud security asymmetry

We in the security world have to make people understand this issue.

My book, Trust in Computer Systems and the Cloud, is due out in the next few weeks, and I was wondering as I walked the dogs today (a key part of the day for thinking!) what the most important message in the book is. I did a bit of thinking and a bit of searching, and decided that the following two paragraphs expose the core thesis of the book. I’ll quote them below and then explain briefly why (the long explanation would require me to post most of the book here!). The paragraph is italicised in the book.

A CSP [Cloud Service Provider] can have computational assurances that a tenant’s workloads cannot affect its hosts’ normal operation, but no such computational assurances are available to a tenant that a CSP’s hosts will not affect their workloads’ normal operation.

In other words, the tenant has to rely on commercial relationships for trust establishment, whereas the CSP can rely on both commercial relationships and computational techniques. Worse yet, the tenant has no way to monitor the actions of the CSP and its host machines to establish whether the confidentiality of its workloads has been compromised (though integrity compromise may be detectable in some situations): so even the “trust, but verify” approach is not available to them.”

What does this mean? There is, in cloud computing, a fundamental asymmetry: CSPs can protect themselves from you (their customer), but you can’t protect yourself from them.

Without Confidential Computing – the use of Trusted Execution Environments to protect your workloads – there are no technical measures that you can take which will stop Cloud Service Providers from looking into and/or altering not only your application, but also the data it is processing, storing and transmitting. CSPs can stop you from doing the same to them using standard virtualisation techniques, but those techniques provide you with no protection from a malicious or compromised host, or a malicious or compromised CSP.

I attended a conference recently attended by lots of people whose job it is to manage and process data for their customers. Many of them do so in the public cloud. And a scary number of them did not understand that all of this data is vulnerable, and that the only assurances they have are commercial and process-based.

We in the security world have to make people understand this issue, and realise that if they are looking after our data, they need to find ways to protect it with strong technical controls. These controls are few:

  • architectural: never deploy sensitive data to the public cloud, ever.
  • HSMs: use Hardware Security Modules. These are expensive, difficult to use and don’t scale, but they are appropriate for some sensitive data.
  • Confidential Computing: use Trusted Execution Environments (TEEs) to protect data and applications in use[1].

Given my interest – and my drive to write and publish my book – it will probably come as no surprise that this is something I care about: I’m co-founder of the Enarx Project (an open source Confidential Computing project) and co-founder and CEO of Profian (a start-up based on Enarx). But I’m not alone: the industry is waking up to the issue, and you can find lots more about the subject at the Confidential Computing Consortium‘s website (including a list of members of the consortium). If this matters to you – and if you’re an enterprise company who uses the cloud, it almost certainly already does, or will do so – then please do your research and consider joining as well. And my book is available for pre-order!

Win a copy of my book!

What’s better than excerpts? That’s right: the entire book.

As regular readers of this blog will know, I’ve got a book coming out with Wiley soon. It’s called “Trust in Computer Systems and the Cloud”, and the publisher’s blurb is available here. We’ve now got to the stage where we’ve completed not only the proof-reading for the main text, but also the front matter (acknowledgements, dedication, stuff like that), cover and “praise page”. I’d not heard the term before, but it’s where endorsements of the book go, and I’m very, very excited by the extremely kind comments from a variety of industry leaders which you’ll find quoted there and, in some cases, on the cover. You can find a copy of the cover (without endorsement) below.

Trust book front cover (without endorsement)

I’ve spent a lot of time on this book, and I’ve written a few articles about it, including providing a chapter index and summary to let you get a good idea of what it’s about. More than that, some of the articles here actually contain edited excerpts from the book.

What’s better than excerpts, though? That’s right: the entire book. Instead of an article today, however, I’m offering the opportunity to win a copy of the book. All you need to do is follow this blog (with email updates, as otherwise I can’t contact you), and when it’s published (soon, we hope – the March date should be beaten), I’ll choose one lucky follower to receive a copy.

No Wiley employees, please, but other than that, go for it, and I’ll endeavour to get you a copy as soon as I have any available. I’ll try to get it to you pretty much anywhere in the world, as well. So far, it’s only available in English, so apologies if you were hoping for an immediate copy in another language (hint: let me know, and I’ll lobby my publisher for a translation!).

Trust book preview

What it means to trust in the context of computer and network security

Just over two years ago, I agreed a contract with Wiley to write a book about trust in computing. It was a long road to get there, starting over twenty years ago, but what pushed me to commit to writing something was a conference I’d been to earlier in 2019 where there was quite a lot of discussion around “trust”, but no obvious underlying agreement about what was actually meant by the term. “Zero trust”, “trusted systems”, “trusted boot”, “trusted compute base” – all terms referencing trust, but with varying levels of definition, and differing understanding if what was being expected, by what components, and to what end.

I’ve spent a lot of time thinking about trust over my career and also have a major professional interest in security and cloud computing, specifically around Confidential Computing (see Confidential computing – the new HTTPS? and Enarx for everyone (a quest) for some starting points), and although the idea of a book wasn’t a simple one, I decided to go for it. This week, we should have the copy-editing stage complete (technical editing already done), with the final stage being proof-reading. This means that the book is close to down. I can’t share a definitive publication date yet, but things are getting there, and I’ve just discovered that the publisher’s blurb has made it onto Amazon. Here, then, is what you can expect.

Learn to analyze and measure risk by exploring the nature of trust and its application to cybersecurity 

Trust in Computer Systems and the Cloud delivers an insightful and practical new take on what it means to trust in the context of computer and network security and the impact on the emerging field of Confidential Computing. Author Mike Bursell’s experience, ranging from Chief Security Architect at Red Hat to CEO at a Confidential Computing start-up grounds the reader in fundamental concepts of trust and related ideas before discussing the more sophisticated applications of these concepts to various areas in computing. 

The book demonstrates in the importance of understanding and quantifying risk and draws on the social and computer sciences to explain hardware and software security, complex systems, and open source communities. It takes a detailed look at the impact of Confidential Computing on security, trust and risk and also describes the emerging concept of trust domains, which provide an alternative to standard layered security. 

  • Foundational definitions of trust from sociology and other social sciences, how they evolved, and what modern concepts of trust mean to computer professionals 
  • A comprehensive examination of the importance of systems, from open-source communities to HSMs, TPMs, and Confidential Computing with TEEs. 
  • A thorough exploration of trust domains, including explorations of communities of practice, the centralization of control and policies, and monitoring 

Perfect for security architects at the CISSP level or higher, Trust in Computer Systems and the Cloud is also an indispensable addition to the libraries of system architects, security system engineers, and master’s students in software architecture and security. 

Review of CCC members by business interests

Reflections on the different types of member in the Confidential Computing Consortium

This is a brief post looking at the Confidential Computing Consortium (the “CCC”), a Linux Foundation project “to accelerate the adoption of Trusted Execution Environment (TEE) technologies and standards.” First, a triple disclaimer: I’m a co-founder of the Enarx project (a member project of the CCC), an employee of Red Hat (which donated Enarx to the CCC and is a member) and an officer (treasurer) and voting member of two parts of the CCC (the Governing Board and Technical Advisory Committee), and this article represents my personal views, not (necessarily) the views of any of the august organisations of which I am associated.

The CCC was founded in October 2019, and is made up of three different membership types: Premier, General and Associate members. Premier members have a representative who gets a vote on various committees, and General members are represented by elected representatives on the Governing Board (with a representative elected for every 10 General Members). Premier members pay a higher subscription than General Members. Associate membership is for government entities, academic and nonprofit organisations. All members are welcome to all meetings, with the exception of “closed” meetings (which are few and far between, and are intended to deal with issues such as hiring or disciplinary matters). At the time of writing, there are 9 Premier members, 20 General members and 3 Associate members. There’s work underway to create an “End-User Council” to allow interested organisations to discuss their requirements, use cases, etc. with members and influence the work of the consortium “from the outside” to some degree.

The rules of the consortium allow only one organisation from a “group of related companies” to appoint a representative (where they are Premier), with similar controls for General members. This means, for instance, that although Red Hat and IBM are both active within the Consortium, only one (Red Hat) has a representative on the Governing Board. If Nvidia’s acquisition of Arm goes ahead, the CCC will need to decide how to manage similar issues there.

What I really wanted to do in this article, however, was to reflect on the different types of member, not by membership type, but by their business(es). I think it’s interesting to look at various types of business, and to reflect on why the CCC and confidential computing in general are likely to be of interest to them. You’ll notice a number of companies – most notably Huawei and IBM (who I’ve added in addition to Red Hat, as they represent a wide range of business interests between them) – appearing in several of the categories. Another couple of disclaimers: I may be misrepresenting both the businesses of the companies represented and also their interests! This is particularly likely for some of the smaller start-up members with whom I’m less familiar. These are my thoughts, and I apologise for errors: please feel free to contact me with suggestions for corrections.

Cloud Service Providers (CSPs)

Cloud Service Providers are presented with two great opportunities by confidential computing: the ability to provide their customers with greater isolation from other customers’ workloads, and the chance to avoid having to trust the CSP themselves. The first is the easiest to implement, and the one on which the CSPs have so far concentrated, but I hope we’re going to see more of the latter in the future, as regulators (and customers’ CFOs/auditors) realise that deploying to the cloud does not require a complex trust relationship with the operators of the hosts running the workload.

  • Google
  • IBM
  • Microsoft

The most notable missing player in this list is Amazon, whose AWS offering would seem to make them a good fit for the CCC, but who have not joined up to this point.

Silicon vendors

Silicon vendors produce their own chips (or license their designs to other vendors). They are the ones who are providing the hardware technology to allow TEE-based confidential computing. All of the major silicon vendors are respresented in the CCC, though not all of them have existing products in the market. It would be great to see more open source hardware (RISC-V is not represented in the CCC) to increase the trust the users can have in confidential computing, but the move to open source hardware has been slow so far.

  • AMD
  • Arm
  • Huawei
  • IBM
  • Intel
  • Nvidia

Hardware manufacturers

Hardware manufacturers are those who will be putting TEE-enabled silicon in their equipment and providing services based on it. It is not surprising that we have no “commodity” hardware manufacturers represented, but interesting that there are a number of companies who create dedicated or specialist hardware.

  • Cisco
  • Google
  • Huawei
  • IBM
  • Nvidia
  • Western Digital
  • Xilinx

Service companies

In this category I have added companies which provide services of various kinds, rather than acting as ISVs or pure CSPs. We can expect a growing number of service companies to realise the potential of confidential computing as a way of differentiating their products and providing services with interesting new trust models for their customers.

  • Accenture
  • Ant Group
  • Bytedance
  • Facebook
  • Google
  • Huawei
  • IBM
  • Microsoft
  • Red Hat
  • Swisscom


There are a number of ISVs (Independent Software Vendors) who are members of the CCC, and this heading is in some ways a “catch-all” for members who don’t necessarily fit cleanly under any of the other headings. There is a distinct subset, however, of blockchain-related companies which I’ve separated out below.

What is particularly interesting about the ISVs represented here is that although the CCC is dedicated to providing open source access to TEE-based confidential computing, most of the companies in this category do not provide open source code, or if they do, do so only for a small part of the offering. Membership of the CCC does not in any way require organisations to open source all of their related software, however, so their membership is not problematic, at least from the point of view of the charter. As a dedicated open source fan, however, I’d love to see more commitment to open source from all members.

  • Anjuna
  • Anqlave
  • Bytedance
  • Cosmian
  • Cysec
  • Decentriq
  • Edgeless Systems
  • Fortanix
  • Google
  • Huawei
  • IBM
  • r3
  • Red Hat
  • VMware


As permissioned blockchains gain traction for enterprise use, it is becoming clear that there are some aspects and components of their operation which require strong security and isolation to allow trust to be built into the operating model. Confidential computing provides ways to provide many of the capabilities required in these contexts, which is why it is unsurprising to see so many blockchain-related companies represented in the CCC.

  • Appliedblockchain
  • Google
  • IBM
  • iExec
  • Microsoft
  • Phala network
  • r3

Trust in Computing and the Cloud

I wrote a book.

I usually write and post articles first thing in the morning, before starting work, but today is different. For a start, I’m officially on holiday (so definitely not planning to write any code for Enarx, oh no), and second, I decided that today would be the day that I should finish my book, if I could.

Towards the end of 2019, I signed a contract with Wiley to write a book (which, to be honest, I’d already started) on trust. There’s lots of literature out there on human trust, organisational trust and how humans trust each other, but despite a growing interest in concepts such as zero trust, precious little on how computer systems establish and manage trust relationships to each other. I decided it was time to write a book on this, and also on how trust works (or maybe doesn’t) in the Cloud. I gave myself a target of 125,000 words, simply by looking at a couple of books at the same sort of level and then doing some simple arithmetic around words per page and number of pages. I found out later that I’d got it a bit wrong, and this will be quite a long book – but it turns out that the book that needed writing (or that I needed to write, which isn’t quite the same thing) was almost exactly this long, as when I finished around 1430 GMT today, I found that I was at 124,939 words. I have been tracking it, but not writing to the target, given that my editor told me that I had some latitude, but I’m quite amused by how close it was.

Anyway, I emailed my editor on completion, who replied (despite being on holiday), and given that I’m 5 months or so ahead of schedule, he seems happy (I think they prefer early to late).

I don’t have many more words in me today, so I’m going to wrap up here, but do encourage you to read articles on this blog labelled with “trust”, several of which are edited excerpts from the book. I promise I’ll keep you informed as I get information about publication dates, etc.

Keep safe and have a Merry Christmas and Happy New Year, or whatever you celebrate.