david wong

Hey ! I'm David, a security consultant at Cryptography Services, the crypto team of NCC Group . This is my blog about cryptography and security and other related topics that I find interesting.

Hash-Based Signatures Part IV: XMSS and SPHINCS December 2015

This post is the ending of a series of blogposts on hash-based signatures. You can find part I here

So now we're getting into the interesting part, the real signatures schemes.

PQCrypto has released an initial recommendations document a few months ago. The two post-quantum algorithms advised there were XMSS and SPHINCS:


This blogpost will be presenting XMSS, a stateful signature scheme, while the next will focus on SPHINCS, the first stateless signature scheme!


The eXtended Merkle Signature Scheme (XMSS) was introduced in 2011 and became an internet-draft in 2015.

The main construction looks like a Merkle tree, excepts a few things. The XMSS tree has a mask XORed to the child nodes before getting hashed in their parents node. It's a different mask for every node:


The second particularity is that a leaf of the XMSS tree is not a hash of a one-time signature public key, but the root of another tree called a L-tree.

A L-tree has the same idea of masks applied to its nodes hashes, different from the main XMSS Trees, but common to all the L-trees.

Inside the leaves of any L-tree are stored the elements of a WOTS+ public key. This scheme is explained at the end of the first article of this series.

If like me you're wondering why they store a WOTS+ public key in a tree, here's what Huelsing has to say about it:

The tree is not used to store a WOTS public key but to hash it in a way that we can prove that a second-preimage resistant hash function suffices (instead of a collision resistant one).

Also, the main public key is composed of the root node of the XMSS tree as well as the bit masks used in the XMSS tree and a L-tree.


SPHINCS is the more recent one, combining a good numbers of advances in the field and even more! Bringing the statelessness we were all waiting for.

Yup, this means that you don't have to keep the state anymore. But before explaining how they did that, let's see how SPHINCS works.

First, SPHINCS is made out of many trees.

Let's look at the first tree:

sphincs layer

  • Each node is the hash of the XOR of the concatenation of the previous nodes with a level bitmask.
  • The public key is the root hash along with the bitmasks.
  • The leaves of the tree are the compressed public keys of WOTS+ L-trees.

See the WOTS+ L-trees as the same XMSS L-tree we previously explained, except that the bitmask part looks more like a SPHINCS hash tree (a unique mask per level).

Each leaves, containing one Winternitz one-time signature, allow us to sign another tree. So that we know have a second layer of 4 SPHINCS trees, containing themselves WOTS+ public keys at their leaves.

This go on and on... according to your initial parameter. Finally when you reach the layer 0, the WOTS+ signatures won't sign other SPHINCS trees but HORS trees.

sphincs structure

A HORST or HORS tree is the same as a L-tree but this time containing a HORS few-time signature instead of a Winternitz one-time signature. We will use them to sign our messages, and this will increase the security of the scheme since if we do sign a message with the same HORS key it won't be a disaster.

Here's a diagram taken out of the SPHINCS paper making abstraction of WOTS+ L-trees (displaying them as signature of the next SPHINCS tree) and showing only one path to a message.


When signing a message M you first create a "randomized" hash of M and a "random" index. I put random in quotes because everything in SPHINCS is deterministically computed with a PRF. The index now tells you what HORST to pick to sign the randomized hash of M. This is how you get rid of the state: by picking an index deterministically according to the message. Signing the same message again should use the same HORST, signing two different messages should make use of two different HORST with good probabilities.

And this is how this series end!

EDIT: here's another diagram from Armed SPHINCS, I find it pretty nice!


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Hash-Based Signatures Part III: Many-times Signatures December 2015

We saw previously what were one-time signatures (OTS), then what were few-time signatures (FTS). But now is time to see how to have practical signature schemes based on hash functions. Signature schemes that you can use many times, and ideally as many times as you'd want.

If you haven't read Part I and Part II it's not necessarily a bad thing since we will make abstraction of those. Just think about OTS as a public key/private key pair that you can only use once to sign a message.

Dumb trees

The first idea that comes to mind could be to use a bunch of one-time signatures (use your OTS scheme of preference). The first time you would want to sign something you would use the first OTS keypair, and then never use it again. The second time you would want to sign something, you would use the second OTS keypair, and then never use it again. This can get repetitive and I'm sure you know where I'm going with this. This would also be pretty bad because your public key would consist of all the OTS public keys (and if you want to be able to use your signature scheme a lot, you will have a lot of OTS public keys).

One way of reducing the storage amount, secret-key wise, is to use a seed in a pseudo-random number generator to generate all the secret keys. This way you don't need to store any secret-key, only the seed.

But still, the public key is way too large to be practical.

Merkle trees

To link all of these OTS public keys to one main public keys, there is one very easy way, it's to use a Merkle tree. A solution invented by Merkle in 1979 but published a decade later because of some uninteresting editorial problems.

Here's a very simple definition: a Merkle tree is a basic binary tree where every node is a hash of its childs, the root is our public key and the leaves are the hashes of our OTS public keys. Here's a drawing because one picture is clearer than a thousand words:

merkle tree

So the first time you would use this tree to sign something: you would use the first OTS public key (A), and then never use it again. Then you would use the B OTS public key, then the C one, and finally the D one. So you can sign 4 messages in total with our example tree. A bigger tree would allow you to sign more messages.

The attractive idea here is that your public key only consist of the root of the tree, and every time you sign something your signature consists of only a few hashes: the authentication path.

In our example, a signature with the first OTS key (A) would be: (1, signature, public key A, authentication path)

  • 1 is the index of the signing leaf. You have to keep that in mind: you can't re-use that leaf's OTS. This makes our scheme a stateful scheme.

  • The signature is our OTS published secret keys (see the previous parts of this series of articles).

  • The public key is our OTS public key, to verify the signature.

  • The authentication path is a list of nodes (so a list of hashes) that allows us to recompute the root (our main public key).

Let's understand the authentication path. Here's the previous example with the authentication path highlighted after signing something with the first OTS (A).


We can see that with our OTS public key, and our two hashes (the neighbor nodes of all the nodes in the path from our signing leaf to the root) we can compute the main public key. And thus we can verify that this was indeed a signature that originated from that main public key.

Thanks to this technique we don't to know all of the OTS public keys to verify that main public key. This saves space and computation.

And that's it, that's the simple concept of the Merkle's signature scheme. A many-times signature scheme based on hashes.

...part IV is here

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Hash-Based Signatures Part II: Few-Times Signatures December 2015

If you missed the previous blogpost on OTS, go check it out first. This is about a construction a bit more useful, that allows to sign more than one signature with the same small public-key/private-key. The final goal of this series is to see how hash-based signature schemes are built. But they are not the only applications of one-time signatures (OTS) and few-times signatures (FTS).

For completeness here's a quote of some paper about other researched applications:

One-time signatures have found applications in constructions of ordinary signature schemes [Mer87, Mer89], forward-secure signature schemes [AR00], on-line/off-line signature schemes [EGM96], and stream/multicast authentication [Roh99], among others [...] BiBa broadcast authentication scheme of[Per01]

But let's not waste time on these, today's topic is HORS!


HORS comes from an update of BiBa (for "Bins and Balls"), published in 2002 by the Reyzin father and son in a paper called Better than BiBa: Short One-time Signatures with Fast Signing and Verifying.

The first construction, based on one-way functions, starts very similarly to OTS: generate a list of integers that will be your private key, then hash each of these integers and you will obtain your public key.

But this time to sign, you will also need a selection function \(S\) that will give you a list of index according to your message \(m\). For the moment we will make abstraction of it.

In the following example, I chose the parameters \(t = 5\) and \(k = 2\). That means that I can sign messages \(m \) whose decimal value (if interpreted as an integer) is smaller than \( \binom{t}{k} = 10 \). It also tells me that the length of my private key (and thus public key) will be of \( 5 \) while my signatures will be of length \( 2 \) (the selection function S will output 2 indexes).


Using a good selection function S (a bijective function), it is impossible to sign two messages with the same elements from the private key. But still, after two signatures it should be pretty easy to forge new ones. The second construction is what we call the HORS signature scheme. It is based on "subset-resilitient" functions instead of one-way functions. The selection function \(S\) is also replaced by another function \(H\) that makes it infeasible to find two messages \(m_1\) and \(m_2\) such that \(H(m_2) \subseteq H(m_1)\).

More than that, if we want the scheme to be a few-times signature scheme, if the signer provides \(r\) signatures it should be infeasible to find a message \(m'\) such that \(H(m') \subseteq H(m_1) \cup \dots \cup H(m_r) \). This is actually the definition of "subset-resilient". Our selection function \(H\) is r-subset-resilient if any attacker cannot find (even with small probability), and in polynomial time, a set of \(r+1\) messages that would confirm the previous formula. From the paper this is the exact definition (but it basically mean what I just said)


so imagine the same previous scheme:


But here the selection function is not a bijection anymore, so it's hard to reverse. So knowing the signatures of a previous set of message, it's hard to know what messages would use such indexes.

This is done in theory by using a random oracle, in practice by using a hash function. This is why our scheme is called HORS for Hash to Obtain Random Subset.

If you're really curious, here's our new selection function:

to sign a message \(m\):

  1. \(h = Hash(m)\)

  2. Split \(h\) into \(h_1, \dots, h_k\)

  3. Interpret each \(h_j\) as an integer \(i_j\)

  4. The signature is \( sk_{i_1}, \dots, sk_{i_k} \)

And since people seem to like my drawings:


...Part III is here

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Hash-Based Signatures Part I: One-Time Signatures (OTS) December 2015


On October 18th 1979, Leslie Lamport published his concept of One Time Signatures.

Most signature schemes rely in part on one-way functions, typically hash functions, for their security proofs. The beauty of Lamport scheme was that this signature was only relying on the security of these one-way functions.


here you have a very simple scheme, where \(x\) and \(y\) are both integers, and to sign a single bit:

  • if it's \(0\), publish \(x\)

  • if it's \(1\), publish \(y\)

Pretty simple right? Don't use it to sign twice obviously.

Now what happens if you want to sign multiple bits? What you could do is hash the message you want to sign (so that it has a predictible output length), for example with SHA-256.

Now you need 256 private key pairs:


and if you want to sign \(100110_2 \dots\),

you would publish \((y_0,x_1,x_2,y_3,y_4,x_5,\dots)\)

Winternitz OTS (WOTS)

A few months after Lamport's publication, Robert Winternitz of the Stanford Mathematics Department proposed to publish \(h^w(x)\) instead of publishing \(h(x)\|h(y)\).


For example you could choose \(w=16\) and publish \(h^{16}(x)\) as your public key, and \(x\) would still be your secret key. Now imagine you want to sign the binary \(1001_2\) (\(9_{10}\)), just publish \(h^9(x)\).

Another problem now is that a malicious person could see this signature and hash it to retrieve \(h^{10}(x)\) for example and thus forge a valid signature for \(1010_2\) (\(10_{10}\)).

This can be circumvented by adding a short Checksum after the message (which you would have to sign as well).

Variant of Winternitz OTS

A long long time after, in 2011, Buchmann et al published an update on Winternitz OTS and introduced a new variant using families of functions parameterized by a key. Think of a MAC.

Now your private key is a list of keys that will be use in the MAC, and the message will dictates how many times we iterate the MAC. It's a particular iteration because the previous output is replacing the key, and we always use the same public input. Let's see an example:

wots variant

We have a message \(M = 1011_2 (= 11_{10})\) and let's say our variant of W-OTS works for messages in base 3 (in reality it can work for any base \(w\)). So we'll say \(M = (M_0, M_1, M_2) = (1, 0, 2)\) represents \(102_3\).

To sign this we will publish \((f_{sk_1}(x), sk_2, f^2_{sk_3}(x) = f_{f_{sk_3}(x)}(x))\)

Note that I don't talk about it here, but there is still a checksum applied to our message and that has to be signed. This is why it doesn't matter if the signature of \(M_2 = 2\) is already known in the public key.

Intuition tells me that a public key with another iteration would provide better security


here's Andreas Hulsing's answer after pointing me to his talk on the subject:

Why? For the 1 bit example: The checksum would be 0. Hence, to sign that message one needs to know a preimage of a public key element. That has to be exponentially hard in the security parameter for the scheme to be secure. Requiring an attacker to be able to invert the hash function on two values or twice on the same value only adds a factor 2 to the attack complexity. That's not making the scheme significantly more secure. In terms of bit security you might gain 1 bit (At the cost of ~doubling the runtime).

Winternitz OTS+ (WOTS+)

There's not much to say about the W-OTS+ scheme. Two years after the variant, Hulsing alone published an upgrade that shorten the signatures size and increase the security of the previous scheme. It uses a chaining function in addition to the family of keyed functions. This time the key is always the same and it's the input that is fed the previous output. Also a random value (or mask) is XORed before the one-way function is applied.


Some precisions from Hulsing about shortening the signatures size:

WOTS+ reduces the signature size because you can use a hash function with shorter outputs than in the other WOTS variants at the same level of security or longer hash chains. Put differently, using the same hash function with the same output length and the same Winternitz parameter w for all variants of WOTS, WOTS+ achieves higher security than the other schemes. This is important for example if you want to use a 128 bit hash function (remember that the original WOTS requires the hash function to be collision resistant, but our 2011 proposal as well as WOTS+ only require a PRF / a second-preimage resistant hash function, respectively). In this case the original WOTS only achieves 64 bits of security which is considered insecure. Our 2011 proposal and WOTS+ achieve 128 - f(m,w) bits of security. Now the difference between WOTS-2011 and WOTS+ is that f(m,w) for WOTS-2011 is linear in w and for WOTS+ it is logarithmic in w.

Other OTS

Here ends today's blogpost! There are many more one-time signature schemes, if you are interested here's a list, some of them are even more than one-time signatures because they can be used a few times. So we can call them few-times signatures schemes (FTS):

So far their applications seems to be reduce to be the basis of Hash-based signatures that are the current advised signature scheme for post quantum usage. See PQCrypto initial recommendations that was released a few months ago.

PS: Thanks to Andreas Hulsing for his comments

Part II of this series is here

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What kind of signature for a post-Quantum world? December 2015

What kind of signature should we choose for the future ?

PQCrypto's initial recommendation, published 3 months ago, recommend using hash-based signatures.

pqcrypto hashed based signatures

Hash-based signatures, or Merkle signatures

The Merkle signature scheme is a digital signature scheme based on hash trees (also called Merkle trees) and one-time signatures such as the Lamport signature scheme. It was developed by Ralph Merkle in the late 1970s and is an alternative to traditional digital signatures such as the Digital Signature Algorithm or RSA.

Reading the SPHINCS whitepaper (a hash-based signature), we can understand a bit more why hash-based signatures were considered by PQCrypto to replace our current quantum weak signatures.

– RSA and ECC are perceived today as being small and fast, but they are broken in polynomial time by Shor’s algorithm. The polynomial is so small that scaling up to secure parameters seems impossible.
– Lattice-based signature schemes are reasonably fast and provide reasonably small signatures and keys for proposed parameters. However, their quanti- tative security levels are highly unclear. It is unsurprising for a lattice-based scheme to promise “100-bit” security for a parameter set in 2012 and to correct this promise to only “75-80 bits” in 2013. Fur- thermore, both of these promises are only against pre-quantum attacks, and it seems likely that the same parameters will be breakable in practice by quantum computers.
– Multivariate-quadratic signature schemes have extremely short signatures, are reasonably fast, and in some cases have public keys short enough for typical applications. However, the long-term security of these schemes is even less clear than the security of lattice-based schemes.
– Code-based signature schemes provide short signatures, and in some cases have been studied enough to support quantitative security conjectures. How- ever, the schemes that have attracted the most security analysis have keys of many megabytes, and would need even larger keys to be secure against quantum computers.

A series of post on hash-based signatures is available here

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Asiacrypt December 2015

Asiacrypt is currently going on in New Zealand (since when NZ is in Asia?)

Program is here (pdf): https://www.math.auckland.ac.nz/~sgal018/AC2015/AC-prog.pdf

it's a two-track event. There are some talks about everything. From Indistinghuishability Obfuscation to Multi Parti Computation. Seems like a good place to be! I'm waiting for videos/slides/reports about the event. Will edit this post accordingly.

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Multilinear maps December 2015

I'm looking at Indistinghuishability Obfuscation (iO). Which seems to be coming from Fully Homomorphic Encryption (FHE), Functional Encryption (FE) and Multilinear Maps (MM).

Watching Sanjam Garg introduction to this iO, I noticed one interesting slide that puts things into context:

  • 2 parties key exchange in 1976 (DH)
  • 3 parties in 2000 (Joux)
  • X parties in 2013 (GGH)


Video here:


Apparently, @Leptan is telling me that all multiparty key exchange using multilinear maps are broken as of today. Cf Cryptanalysis of GGH Map

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Mildly interesting stuff I screenshot November 2015

Sometimes I read something interesting, and so I take a screenshot of it. And I know some people glance at this blog hoping to read a short piece that will provide some good knowledge. So here you go.

Taken from a Dan Bernstein's blogpost:


some history on curves


some constant-time shenanigans


The following is taken from the wikipedia's page on cryptanalysis


some more:


and some more:


And now some history about how the word Entropy was "coined" by Shannon. Taken from Tobin - Entropy, Information, Landauer’s limit and Moore’s law


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Toilet paper and MIT students November 2015

It is possible to repeatedly fold a standard letter-sized sheet of paper at the midway point about six to seven times. In 2012, some MIT students were able to fold an 1.2 kilometer long toilet paper 13 times. And every time the paper was folded, the number of layers on top of each other doubled. Therefore, the MIT students ended up with 2^13 = 8192 layers of paper on top of each other. And poor Eve's job was to manually count all layers one by one.

From Solving the Discrete Logarithm of a 113-bit Koblitz Curve with an FPGA Cluster

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/r/crypto wiki November 2015

There's a subreddit for crypto and it had an empty wiki.

So I filled it.

Below is a copy.

/r/crypto wiki

Please refer to this Wiki before asking questions that might have been asked before (use your common sense).

Cryptography is also usually more interesting than decrypting your random ciphertext, so consider that when posting, read what we are sharing first to see if it's really pertinent.

How to learn about Cryptography?

The first thing you should do, is to sign-up for Dan Boneh's course Crypto I on Coursera.

You do not have to finish it. Watching a few videos will already give you an idea of what is crypto and how easy/hard it is for you. If you can finish the course, and enjoy it at the same time, then you're in for a lot of fun.

Don't try signing-up for Crypto II though.

Alright, that was interesting, MOAR

There are many ways to learn more about crypto. Here's a non-exhaustive list:

But my favorite way: read whitepapers. Look at the ePrint archives and check what papers interest you. Often papers will come with an introduction section that explains the basics.

What about studying cryptography in a real school?

First, it's important to cultivate your new passion. Don't let your course get in the way of reading or building and doing side projects involving crypto.

Second, You need either a bachelor in mathematics or computer science. Depending on which part you find the more interesting in crypto. Usually Math => Theorical Cryptography, CS => Applied Cryptography.

Now either you don't have a master, and you could choose to do a cryptography master. There are a few: Rennes, Bordeaux, Limoges in France.Stanford, etc...

Or you can do a Computer Science or Number Theory oriented master and pick a crypto subject for a phd. Note that a phd will often lead you into theorical research in university, although some phd can be done within a company and might involve applied crypto. But companies around the world might find that relatively relevant (in France a phd will get you to some places).

It's important to know what you want to do, theorical or applied or in the middle? Usually finding an internship in a applied crypto company helps to get out of academia for a while. A good way to see what please you the most. And good news, in cryptography internships are pretty easy to find (at least at the moment).

Alright I'm studying crypto now, how to get more involved?

Cryptography is a big world, many things are happening and it's sometimes hard to follow everything. Especially some mediums give you a high noise-to-quality ratio. So here they are:

  • Check some mailing lists in your field of interest (metzdown, ietf, cfrg, curves, modern crypto, etc...)

  • Follow conventions (listed here on the IACR website). Look out for ECC, Crypto, Asiacrypt, Eurocrypt, Real World Crypto, CHES, etc...

  • Blogs

  • Twitter. Look for cryptographers and check out for interesting discussions and/or links they share.

  • CTFs (and their write-ups)

Where to work in crypto?

Now is your time to find an internship or a job? Apply everywhere, in the world. But where? Where other cryptographers are working, or have worked. You can find that on their published papers (usually written in the header), on Twitter, on Linkedin, etc...

Another good way is to check for "who's hiring" posts on hackernews or reddit

Iacr also list a number of positions here.

Finally, universities around the world usually have room for internships as long as you don't mind not being paid.

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About the easiness of SVP November 2015

First of all, we stress that SVP and its variants should all be considered easy when the lattice dimension is less than 70. Indeed, we will see in Section 4 that exhaustive search techniques can solve SVP within an hour up to dimension 60. But because such techniques have exponential running time, even a 100-dimensional lattice is out of reach. When the lattice dimension is beyond 100, only approximation algorithms like LLL, DEEP and BKZ can be run.

I can't remember from what article I got that from. Must have been something Phong Nguyen wrote.

It states that a lattice of dimension 60 could be easily solved, in an hour, by an exhaustive search (or similar techniques (enumeration?)). Something to dig into.

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I'm back! Oh and also: my master defense November 2015

So I'm now completely out of the loop, because I've been traveling a bunch. If you have any interesting crypto paper/blog post that was released in these last couple of months please post it here :)

Also I obtained my master. If you speak french or are just curious, you can check that here:

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ECC 2015 in Bordeaux October 2015


After defending my master thesis in Labri's amphitheatrum I thought I would never have to go back there again. Little did I know, ECC 2015 took place in the exact same room. I was back in school.



It was a first for me, but for many people it was only one more ECC. Most people knew each other, a few were wandering alone, mostly students. The atmosphere was serious although relaxed. People were mostly in their late 30s and 40s, a good part was french, others came from all over the world, a good minority were government people. Rumor has it that NSA was somewhere hidden.


Nothing really groundbreaking was introduced, as everybody knows ECC is more about politics than math these days. The content was so rare that a few talks were not even talking about ECC. Like that talk about Logjam (was a good talk though) or a few about lattices.

Rump Session



We got warmed up by a one hour cocktail party organized by Microsoft, by 6pm most people were "canard" as the belgium crypto people were saying. We left Bordeaux's Magnificient sun and sat back into the hot room with our wine glasses. Then every 5 minutes a random person would show up on stage and present something, sometimes serious, sometimes ridiculous, sometimes funny.


The panel was introduced by Benjamin Smith and was composed of 7 figures. Dan Bernstein that needs no introduction, Bos from NXP, Flori from the french government agency ANSSI, Hamburg from Cryptography Research (who was surprised that his company let him assist to the panel), Lochter from BSI (German government) and Moody from NIST.


It was short and about standardization, here are the notes I took then. Please don't quote anything from here, it's inexact and redacted after the fact.

  • Presenter: you have very different people in front of you, you have exactly 7 white people in front of you, hopefuly it will be different next year.

  • The consensus is that standardisation in ECC is not working at all. Maybe it should be more like the AES one. Also, people are disapointed that not enough academics were involved... general sadness.

  • Lochter: it's not good to change too much, things are working for now and Post-Quantum will replace ECC. We should start standardizing PQ. Because everything is slow, mathematics takes years to get standardized, then implemented, etc... maybe the problem is not in standardization but keeping software up-to-date.

  • Hamburg: PQ is the end of every DLP-based cryptosystem.

  • Bos: I agree we shouldn't do this (ECC2015) too often. Also we should have a framework where we can plugin different parameters and it would work with any kind of curves.

  • Someone: why build new standards if the old/current one is working fine. This is distracting implementers. How many crypto standards do we already have? (someone else: a lot)

  • Bos: Peter's talk was good (about formal verification, other panelists echoed that after). It would be nice for implementers to have tools to test. Even a database with a huge amount of test vectors would be nice

  • Flori: people don't trust NIST curves anymore, surely for good reasons, so if we do new curves we should make them trustable. Did anyone here tried generating nist, dan, brainpool etc...? (3 people raised their hands).

  • Bernstein: you're writing a paper? Why don't you put the Sage script online? Like that people won't make mistakes or won't run into a typo in your paper, etc...

  • Lochter: people have to implement around patents all the time (ranting).

  • Presenter: NSA said, if you haven't moved to ECC yet, since there will be PQ, don't get into too much trouble trying to move to ECC. Isn't that weird?

  • Bernstein: we've known for years that PQ computers are coming. There is no doubt. When? It is not clear. NSA's message is nice. Details are weird though. We've talked to people at the NSA about that. Really weird. Everybody we've talked to has said "we didn't see that in advance" (the announcement). So who's behind that? No one knows. (someone in the audience says that maybe the NSA's website got hacked)

  • Flori: I agree it's hard to understand what the NSA is saying. So if someone in the audience wants to make some clarification... (waiting for some hidden NSA agent to speak. No one speaks. People laugh).

  • Hamburg: usually they say they do not deny, or they say they do not confirm. This time they said both (the NSA about Quantum computers).

  • Lochter: 30 years is the lifetime of secret data, could be 60 years if you double it (grace period?). We take the NSA's announcement seriously, satelites have stuff so we can upgrade them with curves (?)

  • Presenter: maybe they (the NSA) are scared of all the curve standardization happening and that we might find a curve by accident that they can't break. (audience laughing)

  • Bos: we have to follow standards when we implement in smartcards...

  • Lochter: we can't blame the standard. Look at Openssl, they did this mess themselves.

  • Moody: standards give a false sense a security but we are better with them than without (lochter looks at him weirdly, Moody seems embarassed that he doesn't have anything else to say about it).

  • Bernstein: we can blame it on the standard!

  • Lochter: blame the process instead. Implementers should get involved in the standardization process.

  • Bernstein: I'll give you an example of implementers participating in standardization, Rivest sent a huge comment to the NIST ("implementers have enough rope to hang themselve"). It was one scientific involved in the standardization.

  • Presenter: we got 55 minutes of the panel done before the first disagreement happened. Good. (everybody laughs)

  • Bos: we don't want every app dev to be able to write crypto. It is not ideal. We can't blame the standards. We need cryptographers to implement crypto.
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