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Concurrent Algorithms and Data Structures course of the University of Oxford by 
Ciro Santilli 34 Updated 2024-12-15 +Created 2024-10-23
Ciro Santilli 34 Updated 2024-12-15 +Created 2024-10-23Materials paywalled. E.g.: www.cs.ox.ac.uk/teaching/courses/2023-2024/cads/
TODO clear example and application.
www.quantamagazine.org/quantum-memory-proves-exponentially-powerful-20241016/ from Quanta Magazine has an incomprehensible news of something that sounds cool
On Friday 18th October 2024, Ciro Santilli received a call from Barclays asking where some of the money in his Barclays account came from and went to, obviously linked to the Monero donation and sale.
The following day, the 19th, a "explain your income in 30 days or you'll lose you account" letter arrived, dated from the 8th of October. This had been available on the online documents, but Ciro did not get an email for it so he was unaware.
The following Tuesday, the 22nd, Ciro noticed that all payments from his card were being declined, and upon calling Barclays they said that this was for pending regulatory issues. His account had been frozen.
The following Tuesday, 29th of November, Ciro noticed that a regular payment had gone through. He then tested his card and it was working again, so at some point the account had been unfrozen.
Part of me wants the donor to give me his real identity and sort this out. It would likely be better for the OurBigBook Project. But the other part of me wants to test the British monetary system. Fun and stressful times.
The chaotic nature of Barclays' Know your customer is apparent:
- they took 6 months to flag anything
- once it was finally flaggedAlso, they freeze accounts of people who are still obviously in the country at their home address and making regular purchases locally as before. Not exactly how a criminal would act?
- their communication is a mess:
- the letter was messy, with unclear list of transactions at some points and several typos
- there was no clear notice that the account was frozen or unfrozen. While there can be a rationale for not giving notice before the freeze to prevent criminals from fleeing, once you freeze a regular account user will find it out mighty fast, so there is no point in not notifying them about it
- they block the account days after the online document had been available (which unfortunately Ciro did not see due to lack of email notification), but before you've had the time to reply. This achieves the worst of both worlds both worlds by:
- giving time for criminals to escape
- while also unnecessarily blocking legal accounts before they could provide evidence requested
- their communication is a mess:
It is also slightly fun, but not surprising, to see the AgoraDesk buyers refuse to give any contact besides their public Telegram, not even email. I'm not sure that Barclays does Telegram! Not super important though because ultimately the initial Monero donation is anonymous. Shame I started on AgoraDesk before finding out about cryptocurrency swappers such as SimpleSwap.
De-banking is apparently a widespread issue in the UK: www.uktech.news/fintech/revolut-good-reason-debank-20240909: e.g. www.uktech.news/fintech/revolut-good-reason-debank-20240909 notably mentions a well known base by, God forgive me, Nigel Farage.
Related cases:
How Does International Money Transfer Work?
In simple terms, an international money transfer is a process of sending money from one country to another. When you want to transfer money from Canada to a different country, you pay a service provider the amount in Canadian dollars (CAD), and they convert and send the equivalent amount in the local currency of the destination country.
You can send money through various methods, including:
Banks:
Money transfer operators (like Western Union, MoneyGram)
Online money transfer services (Wise, Remitbee etc...)
Cryptocurrency transfers
Best Ways to Send Money from Canada
In the digital era, there are many ways to send money internationally. Each method offers different advantages, depending on your priority—whether it's speed, cost, or convenience.
Online money transfer services (Wise, Remitbee etc...)
Cryptocurrency transfers
Best Ways to Send Money from Canada
In the digital era, there are many ways to send money internationally. Each method offers different advantages, depending on your priority—whether it's speed, cost, or convenience.
Banks
Traditional banks remain a popular method for sending money abroad, but they are often the most expensive. Banks usually charge higher fees and offer less competitive exchange rates compared to online services. However, if you prefer working with established institutions, they may be a good option for you. Keep in mind that it may take a few days for the transfer to complete.
Traditional banks remain a popular method for sending money abroad, but they are often the most expensive. Banks usually charge higher fees and offer less competitive exchange rates compared to online services. However, if you prefer working with established institutions, they may be a good option for you. Keep in mind that it may take a few days for the transfer to complete.
Online Money Transfer Services:
These services are often the best for low-cost and fast transfers. Services like Wise (formerly TransferWise), PayPal, and Remitly offer much better exchange rates than banks. Additionally, they charge minimal fees, and the transfers are usually completed within minutes to hours, depending on the destination.
Money Transfer Operators:
Companies like Western Union and MoneyGram have been in the game for a long time, allowing customers to send money in-person or online. They offer a wide network of locations, but their fees can be relatively high, and exchange rates might not always be the best.
Cryptocurrency:
If you're familiar with crypto, sending money through Bitcoin, Ethereum, or other cryptocurrencies might be a convenient and low-cost option. However, this method requires some understanding of how crypto wallets work and may not be suitable for everyone.
Key Factors to Consider for International Money Transfers
Whether you’re sending money to family in India or making a business payment to Europe, it’s essential to understand the key factors that can affect your international money transfer.
Whether you’re sending money to family in India or making a business payment to Europe, it’s essential to understand the key factors that can affect your international money transfer.
Exchange Rates:
The exchange rate determines how much your money will be worth in the recipient’s currency. Providers typically mark up the exchange rate, which means they take a percentage of the amount being transferred. Comparing exchange rates between different providers can save you a lot of money in the long run.
Pro tip: Use online comparison tools to find the best exchange rates before making a transfer.
Transfer Fees:
Depending on the service you choose, there will be transfer fees involved. Banks typically charge higher fees, especially if you’re sending money to a country with a different currency. Online services usually have lower fees, but it’s essential to read the fine print—some may have hidden charges, especially for quick transfers.
Speed of Transfer:
If you need to send money quickly, the speed of the transfer is a big factor. Some services offer instant international money transfers, while others may take several days. In general, online money transfer services tend to be faster than banks.
Transfer Limits:
Check if there are any limitations on how much you can send. Some services have a maximum limit for each transfer, while others allow you to send larger sums. This can be an important consideration if you’re making a significant payment, like purchasing a property or paying tuition fees abroad.
Security and Regulation:
Ensure that the service you choose is regulated and offers adequate security. Trusted money transfer providers will use encryption and other security measures to protect your data. Additionally, it’s wise to check if the provider is regulated by the Canadian government or international bodies, as this adds another layer of security.
Welcome to my home page!
Symmetric encryption is a type of encryption where you use a password (also known as a "key") to encrypt your data, and then the same password to decrypt the data.
For example, this is the type of encryption that is used for encrypting the data in our smartphones and laptops with disk encryption.
This way, if your laptop gets stolen, the thief is not able to see your private photos without knowing your password, even though they are able to read every byte of your disk.
The downside is that that you have to type your password every time you want to login. This leads people to want to use shorter passwords, which in turn are more prone to password cracking.
The other main type of encryption is public-key cryptography.
The advantage of public-key cryptography is that it allows you to send secret messages to other people even an the attacker is able to capture the encrypted messages. This is for example what you want to do when sending a personal message to a friend over the Internet. Such encryption is especially crucial when using wireless communication such as Wi-Fi, where anyone nearby can capture the signals you send and receive, and would be able to read all your data if it weren't encrypted.
Easily sending encrypted messages over the Internet is not possible with symmetric encryption because for your friend to decrypt the message in that system, you'd need to send them the password, which the attacker would also be able to eavesdrop and then decrypt the message that follows using it. The problem of sharing a password with another person online is called key exchange.
Advanced Encryption Standard (AES) is one of the most popular families of symmetric encryption algorithms.
OpenSSL is a popular open source implementation of symmetric and public-key cryptography. A simple example of using OpenSSL for symmetric encryption from the command-line is:This asks for a password, which we set as contains:Then to decrypt:once again asks for your password and given the correct password produces a file This was tested on Ubuntu 24.04, OpenSSL 3.0.13. See also: How to use OpenSSL to encrypt/decrypt files? on Stack Overflow.
echo 'Hello World!' > message.txt
openssl aes-256-cbc -a -salt -pbkdf2 -in message.txt -out message.txt.encasdfqwer, and then produces a file message.txt.enc containing garbled text such that:hd message.txt.enc00000000 55 32 46 73 64 47 56 6b 58 31 38 58 48 65 2f 30 |U2FsdGVkX18XHe/0|
00000010 70 56 42 2b 70 45 6c 55 59 38 2b 54 38 7a 4e 34 |pVB+pElUY8+T8zN4|
00000020 4e 37 6d 52 2f 73 6d 4d 62 64 30 3d 0a |N7mR/smMbd0=.|
0000002dopenssl aes-256-cbc -d -a -pbkdf2 -in message.txt.enc -out message.new.txtmessage.new.txt containing the original message:Hello World!There is no provably secure symmetric-key algorithm besides the one-time pad, which has the serious drawback of requiring the key to be as long as the message. This means that we believe that most encryption algorithms are secure because it is a hugely valuable target and no one has managed to crack them yet. But we don't have a mathematical proof that they are actually secure, so they could in theory be broken by new algorithms one day.
Pinned article: ourbigbook/introduction-to-the-ourbigbook-project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivative - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 2. You can publish local OurBigBook lightweight markup files to either OurBigBook.com or as a static website.
Figure 3. Visual Studio Code extension installation.
Figure 4. Visual Studio Code extension tree navigation.
Figure 5. . You can also edit articles on the Web editor without installing anything locally. Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.Video 4. OurBigBook Visual Studio Code extension editing and navigation demo. Source. - Internal cross file references done right:
- Infinitely deep tables of contents:
Figure 6. Dynamic article tree with infinitely deep table of contents.Live URL: ourbigbook.com/cirosantilli/chordateDescendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact