Further Functional Analysis course of the University of Oxford by 
Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16
Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16- 2023: courses.maths.ox.ac.uk/course/view.php?id=5033. Open with solutions.
Quantum Processes and Computation course of the University of Oxford 2024-2025 by Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16
Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16 Quantum Processes and Computation course of the University of Oxford 2023-2024 by Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16
Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16 Graph Representation Learning course of the University of Oxford by Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16
Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16 Concurrent Algorithms and Data Structures course of the University of Oxford by Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16
Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16Materials 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
Sponsor Ciro Santilli's work on OurBigBook.com 1000 Monero donation Barclays regulation by Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16
Ciro Santilli 37 Created 2024-10-23 Updated 2025-07-16On 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:
- 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:
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.
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