Chinese government idolatry in a time of the coronavirus

I just found this video about some people’s initial responses to the coronavirus in China. The idolatry for the Chinese government, within China, is very remarkable: “Not afraid! We have our government, government can protect us!”

Protecting your privacy: asymmetric cryptography (part 2)

This is the second of four posts in which I discuss cryptography. If you read all four posts, you will understand the differences between symmetric and asymmetric cryptography, why the US government were against the spread of modern cryptography, how it has resulted in the first crypto war between code rebels (techno-libertarians) and the US government, and how you can easily protect your privacy using Pretty Good Privacy (PGP).

The topics of the four posts are:

  1. What is symmetric cryptography;
  2. What is asymmetric (public key) cryptography;
  3. The first crypto war between code rebels and the government;
  4. How to easily use PGP to protect your e-mail communication.

What is asymmetric (public key) cryptography

In my previous post, I mentioned four disadvantages of symmetric cryptography. These disadvantages are:

  1. The secret key must be shared between sender and receiver, before messages can be exchanged safely, preferably over a secure channel.
  2. The secret key is in two separate places.
  3. The sender of the message must trust the receiver that he will not steal or copy the secret key.
  4. It is not scalable for, for example, e-commerce.

Soon after the publication of the Data Encryption Standard (DES), asymmetric (public key) cryptography was invented by the Stanford graduate student, Whitfield Diffie, and Stanford Professor, Martin Hellman. This was a huge revolution within cryptographic research, because up until then it was thought that there should always be a shared secret key for the communication between the sender and receiver. The main question that Diffie and Hellman were trying to solve was: how can you create secure communication over a unsecure channel, when two corresponding people have never had contact with one another and therefore have not yet been able to share secret keys with each other.

The solution, public key cryptography, was introduced by Diffie and Hellman in their paper, ‘New Directions in Cryptography’ (1976). It inspired more cryptographic research outside the circles of secret agencies. Soon after the first publication on public key cryptography, three young Professors at MIT, Ron Rivest, Adi Shamir and Leonard Adleman, developed the now famous RSA public key cryptosystem in 1977.

Merkle Diffie Hellman
Ralph Merkle, Martin Hellman, and Whitfield Diffie. Merkle is known for his invention of Merkle trees, which is a tree-like structure of cryptographic hashes that organizes for example Bitcoin transactions. The public key cryptosystem, as published in ‘New Directions in Cryptography’, is mostly known as the Diffie-Hellman key exchange. Hellman, however, recognizes the contributions of Merkle for the Diffie-Hellman key exchange.
Adi Shamir, Ron Rivest, and Len Adleman. Inventors of the RSA cryptosystem.

Public key cryptography works as follows. There are two separate keys that correspond mathematically with one another: the public key and the private key. The public key is used to encrypt a message, and can be shared to other people. The private key is used to decrypt a message, and should be kept secret. Public key cryptography is hence a two way function. Just by knowing someone’s public key, it’s not possible to find out the person’s private key.

In our below example,

  1. Alice would like to send a secret love message to Bob.
  2. Bob has a corresponding public an private key, and sends the public key over a unsecure channel to Alice.
  3. Alice uses Bob’s public key to encrypt her secret love message.
  4. Alice sends the secret love message to Bob.
  5. Bob uses the corresponding private key to decrypt the message and finds out that Alice loves him.
Public Key cryptography
Alice and Bob use public key cryptography to exchange secret messages.

Doing so, you can have private correspondence over an unsecure channel. Actually, we’re using public key cryptography all the time. Whenever you see a green padlock in front of the URL bar, it means that the data you enter on the website is first encrypted before it’s sent out.

Digital Signatures

Public key cryptography is not only used for the encryption and decryption of messages, but also for message authentication. If Alice would not have encrypted her message with Bob’s public key, but with her own private key, then the encrypted message can be decrypted with her public key. If you receive a message of John Locke and you’d like to know whether it’s really sent out by Locke, then you could look up his public key and use it to decrypt his message. If the result is plaintext, and assuming that Locke is the only person in the world who possesses the only private key that can produce the encrypted message, you can be sure that the message was sent by Locke. In other words: applying a private key to a message is the equivalent to putting a digital signature.

Digital Signatures
Alice puts a digital signature on her message, and Bob digitally verifies that the message is truly coming from Alice. This is an easy way of using digital signatures. In reality, a text is hashed first with a hash algorithm, before it is encrypted with the private key. Bob then uses Alice’s public key to decrypt the message to retrieve the hash, and compares the resulting hash with the original hash of Alice’s message.

Digital signatures are particularly important, because they provide the following security aspects:

  1. Authentication: it offers proof that the message comes from the right person.
  2. Non-repudiation: we cannot deny that the signee has sent it.
  3. Data integrity: the message cannot be altered after it has been signed.

Diffie and Hellman saw great potential for public key cryptography in the coming digital age. The US secret intelligence, however, were not happy with this development in cryptography and tried to prevent public use of this new cryptosystem. The standoff between privacy advocates of whom many were cryptographers and the US government is known as the first crypto war.

In part three of this series, we will discuss the crypto war. Eventually, at the end of the post series, you will be able to encrypt your e-mails using public key cryptography.

The Blockchain Basics Book has been published and is available for free

Our Blockchain Basics book (Blockchain Basisboek in Dutch) has just been published on January 17th. You can download it here for free. The book will be used in classrooms across more than 8 local universities in the Netherlands. Hopefully, other universities will follow soon.

In this post, I’d like to discuss why I started the initiative to write the ±550 pages book, and what other project I have in mind to further improve blockchain education in the Netherlands.


The current state of blockchain education in the Netherlands

After two months of teaching blockchain at a local Dutch university, October 2018, I realized that blockchain education in the Netherlands (probably in most parts of the world) is still lacking.

I have identified the following 7 issues with our blockchain education in the Netherlands.

Blockchain education in Netherlands
Issues in the Dutch blockchain education space.
  1. Few Dutch class material. Good blockchain content is mostly written in the English language. My required reading list therefore consists mainly of English material, which proves to be a high barrier for Dutch-speaking students that are not at all familiar with (a) the technology and (b) the technical jargon used in the blockchain space.
  2. Dutch content is dispersed. Good content in Dutch is very dispersed among many different websites.
  3. Current Dutch books are not very useful for educational purposes. The books available on the Dutch market are not comprehensive enough and are not suitable for students.
  4. There is no standard for good blockchain education. Most universities are developing curricula on their own and there’s no standard on what good blockchain education consists of.
  5. Few sparring partners. Most universities don’t share their class materials or experiences teaching blockchain. Fortunately, the Dutch Blockchain Coalition is trying to change this, but we need to put much more effort to do cross-institutional sharing. Many universities also want to develop blockchain education, but lack the expertise. It would be good if these universities jointly develop their blockchain curriculum with other universities and share teachers.
  6. Knowledge is dispersed. Different faculties within a university are developing blockchain education in isolation and have their own blockchain experts who don’t know that some of their colleagues are also working on blockchain. Someone who’s working on the legal side of blockchain may not know that there’s someone at another faculty who is working on the technical or ethical side of blockchain. Bringing knowledge from different people together can lead to interesting and surprising new perspectives.
  7. Not enough diversity in perspectives. Blockchain can be approached from many different perspectives. Most classes only focus on a limited number of perspectives. A business department may heavily focus on blockchain applications and little on the technical side. Not knowing the technical side of blockchain, a business teacher may talk about potential blockchain applications and develop business models that are technically unfeasible.

I wrote the Blockchain Basics book, together with my colleague Arthur Janse, to tackle the first 3 issues (in green).

Main topics of the book

The book comprises three parts:

  1. Part I contains the technical side of blockchain and relevant innovations. Topics that we discuss are Bitcoin, current payment systems, consensus protocols, mining, nodes, forks, cryptography, smart contracts, governance, cryptoeconomics, and self-sovereign identities.
  2. Part II contains the economic and philosophical background of the Bitcoin blockchain. It discusses the different economic schools and in particular how the Austrian School of Economics and libertarianism, crypto-anarchism and cypherpunk have influenced Bitcoin.
  3. Part III contains topics revolving around enterprise blockchain. It discusses decentralized business models and enterprise applications.

What’s next?

While writing the book, I came up with the idea to create an organic community based open access digital knowledge platform that anyone can join for free. I pitched the idea in September 2019 at a Dutch Blockchain Coalition (DBC) event for all universities in the Netherlands. The DBC and other universities responded enthusiastically. Four months later, we have a proposal ready to develop the platform with 6 universities and the DBC.

We would like to use the Blockchain Basics book as the foundation of the platform, and – acknowledging that knowledge is decentralized – give all users the right to add new or revise already existing content. A public reviewing feature and a reputation system will be put in place to make sure that wrong content becomes corrected and to incentivize users to add good content. Students can also submit their Bachelor, Master and PhD dissertations and researchers can submit their papers on the platform. 

I think that the multidisciplinary and cross-institutional cooperation will structurally improve blockchain education in the Netherlands. Doing so, I think we can tackle all the other issues (issues number 4 – 7).

Protecting your privacy: symmetric cryptography (part 1)

In my previous post, I discussed the decline of internet freedoms around the world. While writing the post, I realized that I should follow-up on the topic and discuss how we can use cryptography to protect our communication from surveillance by governments and corporations.

This is the first of four posts in which I discuss cryptography. If you read all four posts, you will understand the differences between symmetric and asymmetric cryptography, why the US government were against the spread of modern cryptography, how it has resulted in the first crypto war between code rebels (techno-libertarians) and the US government, and how you can easily protect your privacy using Pretty Good Privacy (PGP).

The topics of the four posts are:

  1. What is symmetric cryptography;
  2. What is asymmetric (public key) cryptography;
  3. The first crypto war between code rebels and the government;
  4. How to easily use PGP to protect your e-mail communication.

What is symmetric cryptography

The use of cryptography is more than 4,000 years old. A classic example of symmetric cryptography is the Caesar cipher. It was used by Julius Caesar for his private correspondence with his generals.

The principle of the Caesar cipher is simple. The receiver of the message has to replace each letter with another letter, some number of fixed positions down the alphabet. If a Caesar cipher, for example, makes use of a rotation of three to the left,

  • A in the encrypted text becomes X
  • C becomes Z
  • E becomes B
  • etc…
Caesar cipher
Caesar cipher: rotation of three to the left.

A Caesar cipher, compared to modern encryption methods, can be easily deciphered. You can for example make a frequency analysis of letters and see whether the letters in the encrypted text resemble typically Dutch or English writing. Also, each letter in the encrypted text only has 26 possibilities in the decrypted text, including itself. You can also make a table in which you write down the text and let a computer replace each letter with all 26 possibilities.

Up until the 1970s, cryptographers made use of this type of cryptography – also known as symmetric cryptography.

With symmetric cryptography, there is one key (the secret key) that is used for encrypting and decrypting the message. It’s therefore necessary for the sender of the message to share the secret key with the party he would like to correspond with.

The Caesar cipher is considered to be symmetric cryptography, because knowing the exact rotation (secret key) that is used to encrypt the message, you do also know how to decrypt the message.

Symmetric cryptography
Symmetric cryptography. One key (the secret key) is used for the encryption and decryption of messages.

Disadvantages of symmetric cryptography

There are several disadvantages to symmetric cryptography.

The first disadvantage is that the secret key has to be shared between the sender and receiver for messages to be exchanged privately. Sending the secret key over an unprotected communication channel is not recommended. In the next post, we will see how asymmetric (public key) cryptography allows us to send the encryption key safely over unprotected communication channels, while keeping the decryption key safely in our own possession.

The second disadvantage is that the secret key is now on two different locations. Thus, there are now two points of attack.

The third disadvantage is that the sender has to trust the receiver that he will not steal or copy the key or give it to someone else. It’s comparable to sharing the keys to your apartment: you also have to trust the other person not to steal your key, or copy your key, or give the key to another person.

The fourth disadvantage is limited scalability. Assuming that we’d like to communicate with a great number of parties, and that we’d like to provide each party with a different secret key for security reasons, we’d need to maintain a database of secret keys. For this setup to be user friendly in an environment like the internet, it would probably require an infrastructure of specialized distribution centers that generate secret keys each time two parties would like to initiate a private conversation. As these distribution centers would hold many secret keys, it would be a honey pot for hackers.

An example of symmetric cryptography is the Data Encryption Standard (DES), which was released on the market in 1975. It was developed by IBM, and was primarily meant to protect electronic communication between large financial organizations. Up until DES, cryptography was mainly a field for governments’ secret intelligence agencies to protect state communication. When the DES was released, it was received very well by cryptographers, until people found out that the National Security Agency (NSA) was involved with the development of the encryption key and purposefully influenced IBM to limit the key sizes from 64 bits to 56 bits. With 56 bits, there are 2^56 possible key combinations. This is considerably less than 64 bits keys. It is therefore much easier to break the encryption. Cryptographers believed that it would just be a matter of time before someone would find the right keys through a brute force search – meaning that you are trying all possible key combinations to find the right one.

Symmetric cryptography was the way cryptography was done until 1976 when two young researchers from Stanford University, Whitfield Diffie and Martin Hellman, invented asymmetric or public key cryptography.

Both researchers were discontent with DES, and Hellman even addressed a letter to the Secretary of Commerce, Elliot Richardson, saying:

I am writing to you because I am very worried that the National Security Agency has surreptitiously influenced the National Bureau of Standards [NBS] in a way which seriously limit the value of a proposed standard, and which may pose a threat to individual privacy. I refer to the proposed Data Encryption Standard. … I am convinced that NSA in its role of helping NBS design and evaluate possible standards has ensured that the proposed standard is breakable by NSA.

In my next post, I will discuss how public key cryptography works. Eventually, at the end of the post series, you will be able to encrypt your e-mails using public key cryptography.

The fight to preserve the internet as a tool of liberty

What’s the state of our internet freedoms around the world? Freedom House (2019) has recently released a report entitled ‘Freedom on the Net 2019‘.

According to the report, more than 3.8 billion people still have no access to the internet, but

  • 71% of those who have access do live in countries where individuals have been arrested and thrown in jail for posting political, social or religious content;
  • 65% live in countries where individuals have been attacked or killed for their online activities;
  • 59% live in countries where authorities use online commentators to manipulate online discussions;
  • 33 out of 65 countries that were assessed have seen their internet freedoms decline over past year.

The greatest declines in internet freedoms happened in Sudan, Kazakhstan, Brazil, Bangladesh and Zimbabwe. For the fourth consecutive year, China has been the greatest abuser of internet freedoms, and although the United States is still scoring well, they have been on decline for three consecutive years.

The ranking from most to least free is as follows:



The report scores the countries, based on the internet controls that are in place:



Governments hold more technological capabilities than ever before to surveil their citizens. They make use of bots to manipulate social media and big data analyses to surveil citizens. See for example this.  In August 2018, Le Dinh Luong has been sentenced to jail for 20 years in Vietnam for addressing and posting about human rights abuses on social media in the country. In March 2019, an Uyghur Muslim was stopped and interrogated for three days, because not HE but someone ELSE on his WeChat contact list had checked in from Mecca.

What was once a liberating technology has now become a conduit for surveillance and electoral manipulation. What can we do to protect our internet liberties?

Small thought on calls for societal discussions on the ethics of cryptosystems

When people say that we should involve society in discussing the ethics of cryptosystems and blockchain, we should ask ourselves why society is suddenly paying attention to the strides we’re making in the cryptospace. Where does this attention come from?

Back in 2011, society was considering us weird and misinformed. Encryption, digital money, anonymous networks, digital pseudonyms, zero knowledge, reputations, information markets, black markets, collapse of governments were spoken about openly in the cryptospace and no one paid much attention.

6-7 years later, after Bitcoin has shown it’s not just a fad, some groups within society have particularly paid close attention to cryptosystems and are now leading the discourse of what they call “discussions for society’s sake”. Who are they and what are their interests? Banks, central banks and national governments. They’re trying to shape the discourse around cryptosystems, because (a) banks are afraid of becoming obsolete by cryptosystems, (b) central banks are afraid of losing control over monetary policy, and (c) governments are afraid that their national currencies will be outcompeted by cryptocurrencies and their inability to tax and trace crypto payments. When they call for societal discussions about the ethics and consequences of cryptosystems, they thus enter the discussions from a position of fear. Can we then really have substantial discussions with them?

Or will they enter the discussions already motivated to overregulate cryptosystems – spoiling everything beautiful about cryptosystems so that their operations are not threatened?

My main point: be careful of those who say we need more public discussions on cryptosystems. Their calls sound noble, but they may have hidden agendas and don’t enter discussions with an open mind to learn about the beauty of cryptosystems.

Example case of this: Benjamin Lawsky and BitLicense.

Follow Hong Kong’s district election

Today is a big day for Hong Kong, as the people are voting for their district representatives. Never before has there been such a high voter turnout: 71.2%. I haven’t found any English website that allows you to follow the results live, so here is a Chinese website:

Yellow is the pro-democracy camp and red is the pro-establishment (pro-Beijing) camp. As of this writing, some results have come in already and the pro-democracy camp is far ahead having occupied more than 90% of the seats (45 against 4).

This is the first stage of the 2019-2020 election cycle. The election will fill 452 seats on Hong Kong’s 18 District Councils. Next year, there will be elections for the territory-wide Legislative Council.

Elections HK screenshot