Mega eTextbooks release thread (part-3)! Find your textbooks here between $5-$25 :)

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Please find the list below:

1. Barron's CCRN Exam: Juarez, APN, CCNS, CCRN-K, Patricia

2. Microeconomics, Student Value, 7th Edition: Jeffrey M. Perloff

3. Cracking the AP Psychology Exam, 2017 Edition: Proven Techniques to Help You Score a 5 (College Test Preparation): Princeton Review

4. Introduction to Abnormal Child and Adolescent Psychology, 3rd Edition: Robert Weis

5. Managerial Economics, 4th Edition: Luke M. Froeb & Brian T. McCann & Michael R. Ward & Mike Shor

6. Writing that Works: Communicating Effectively on the Job: Walter E. Oliu & Charles T. Brusaw & Gerald J. Alred

7. Horngren's Financial & Managerial Accounting, The Financial Chapters, Global 5th Edition: Tracie L. Miller-Nobles & Brenda L. Mattison & Ella Mae Matsumura

8. Biology: The Dynamic Science: Peter J. Russell, Paul E. Hertz, Beverly McMillan

9. CCENT ICND1 100-105 Exam Cram: Anthony Sequeira

10. 31 Days Before Your CCNA Routing & Switching Exam: A Day-By-Day Review Guide for the ICND1/CCENT (100-105), ICND2 (200-105), and CCNA (200-125) Certification Exams: Allan Johnson

11. Global Capitalism: Its Fall and Rise in the Twentieth Century: Jeffry A. Frieden

12. The Origins of the Modern World: A Global and Environmental Narrative from the Fifteenth to the Twenty-First Century (World Social Change), 3rd Edition: Robert B. Marks

13. Transformations: Women, Gender and Psychology, 2nd Edition: Mary Crawford

14. Strategic Compensation: A Human Resource Management Approach, Global 8th Edition, : Joseph J. Martocchio

15. Terrorism in the 21st Century, 7th Edition: Cynthia C. Combs

16. Campbell Biology, Canadian 2nd Edition: Steven A. Wasserman

17. Barron's ACT, 2nd edition (Barron's Act (Book Only)): Brian W. Stewart

18. The Official ACT Prep Guide: ACT

19. Ultimate Guide to the Math ACT: Richard Corn

20. Corporate Communication (Irwin Business Communications), 7th Edition: Paul A Argenti

21. Biological Psychology, 12th Edition: James W. Kalat

22. Financial Accounting: IFRS, 3rd Edition: Jerry J. Weygandt & Paul D. Kimmel & Donald E. Kieso

23. Society and Technological Change, 7th Edition: Rudi Volti

24. Java Foundations: Pearson New International 3rd Edition: John Lewis & Peter DePasquale & Joe Chase

25. University Physics with Modern Physics, 14th Edition: Hugh D. Young & Roger A. Freedman & A. Lewis Ford & Francis Weston Sears

26. Gateways to Art: Understanding the Visual Arts, 2nd Edition: Debra J. DeWitte & Ralph M. Larmann & M. Kathryn Shields

27. Essentials of Abnormal Psychology, 7th Edition: V. Mark Durand & David H. Barlow

28. Finite Mathematics, 6th Edition: Stefan Waner & Steven Costenoble

29. New Perspectives Microsoft Office 365 & Access 2016: Comprehensive: Mark Shellman & Sasha Vodnik

30. Environment: The Science behind the Stories: Jay H. Withgott & Matthew Laposata

31. Digital Planet: Tomorrow's Technology and You, Introductory (Computers Are Your Future), 10th Edition: Ben Beekman & George Beekman

32. Architecture and Interior Design: An Integrated History to the Present: Buie Harwood & Bridget May & Curt Sherman

33. Curren's Math for Meds: Dosages and Solutions, 11th Edition: Anna M. Curren & Margaret Witt

34. The Legal Environment of Business: Text and Cases, 10th Edition: Frank B. Cross & Roger LeRoy Miller

35. Prentice Hall's Federal Taxation 2015 Comprehensive: Thomas R. Pope & Timothy J. Rupert & Kenneth E. Anderson

36. Drug Use and Abuse: A Comprehensive Introduction, 9th Edition: Howard Abadinsky

37. Davis's Canadian Drug Guide for Nurses, 15th Edition: April Hazard Vallerand & Cynthia A Sanoski & Judith Hopfer Deglin

38. Psychology, 12th Edition: Carole Wade & Carol Tavris

39. How to Nurse: Gweneth Hartrick Doane & Colleen Varcoe

40. The Advertising Concept Book: Think Now, Design Later, 3rd Edition: Pete Barry

41. Software, Infrastructure, Labor: A Media Theory of Logistical Nightmares: Ned Rossiter

42. Organic Chemistry, 8th Edition: Paula Yurkanis Bruice

43. Humanities: Culture, Continuity and Change, The, Volume I, 3rd Edition: Henry M. Sayre

44. Financial Accounting, 9th Edition: Robert Libby

45. Preface to Marketing Management, 14th Edition: J. Paul Peter

46. Fundamentals of Differential Equations, 9th Edition: R. Kent Nagle & Edward B. Saff & Arthur David Snider

47. New Dimensions in Women's Health: Linda Lewis Alexander & William Alexander & Judith H. LaRosa & Helaine Bader

48. Essentials of Economics, 10th Edition: Bradley Schiller

49. Purchasing and Supply Management (The Mcgraw-Hill Series in Operations and Decision Sciences), 15th Edition: P. Fraser Johnson

50. Biological Science, 6th Edition: Scott Freeman,Kim Quillin,Lizabeth Allison,Michael Black,Emily Taylor,Author

51. Critical Thinking: A Students Introduction, 5th Edition: Gregory Bassham & William Irwin & Henry Nardone & James Wallace

52. Music for Sight Singing, 6th Edition: Thomas E. Benjamin & Michael Horvit & Robert S. Nelson

53. Microsoft Office 2013: Advanced (Shelly Cashman Series): Misty E. Vermaat

54. Entrepreneurship, 4th Edition: Andrew Zacharakis & William D. Bygrave & Andrew C. Corbett

55. Blockchain: Ultimate guide to understanding blockchain, bitcoin, cryptocurrencies, smart contracts and the future of money: Mark Gates

56. Understanding Computers: Today and Tomorrow, Comprehensive, 16th Edition: Deborah Morley & Charles S. Parker

57. The Boundaries of Australian Property Law: Hossein Esmaeili & Brendan Grigg

58. New Perspectives on Computer Concepts 2016, Introductory: June Jamrich Parsons

59. California Politics and Government: A Practical Approach, 14th Edition: Larry N. Gerston & Terry Christensen

60. Foodservice Organizations: A Managerial and Systems Approach, 8th Edition: Mary B. Gregoire

61. The Elements of Moral Philosophy, 8th Edition: James Rachels

62. Social Science: An Introduction to the Study of Society, 16th Edition: Elgin F. Hunt & David C. Colander

63. Psychiatric Nursing, 7th Edition: Norman L. Keltner & Debbie Steele

64. Microsoft SQL Server 2016: A Beginner's Guide, Sixth Edition (Beginner's Guides): Dusan Petkovic

65. The Analytic Hospitality Executive: Implementing Data Analytics in Hotels and Casinos (Wiley and SAS Business Series): Kelly A. McGuire

66. Diseases of the Human Body, 6th edition: Carol D Tamparo

67. Principles of Corporate Finance (Mcgraw-Hill/Irwin Series in Finance, Insurance, and Real Estate): Richard Brealey

68. Gerontological Nursing, 8th Edition: Charlotte Eliopoulos

69. How to Use SPSS®: A Step-By-Step Guide to Analysis and Interpretation, 9th Edition: Brian C Cronk

70. What is Life? A Guide to Biology, 3rd Edition: Jay Phelan

71. Archaeology: Theories, Methods, and Practice (Seventh Edition): Colin Renfrew & Paul Bahn

72. Problem Solving and Program Design in C, 8th Edition: Jeri R. Hanly & Elliot B. Koffman

73. Economics, 4th Edition: Paul Krugman & Robin Wells

74. Strategic Brand Management, Global 4th Edition: Kevin Keller

75. Winningham's Critical Thinking Cases in Nursing: Medical-Surgical, Pediatric, Maternity, and Psychiatric, 6th Edition: Mariann M. Harding & Julie S. Snyder

76. Maternal-Newborn Nursing The Critical Components of Nursing Care, 2nd Edition: Roberta Durham & Linda Chapman

77. Object-Oriented Software Engineering: An Agile Unified Methodology: David Kung

78. Ebersole and Hess' Gerontological Nursing and Healthy Aging, Canadian 1st Edition: Theris A. Touhy & Kathleen F Jett & Veronique Boscart & Lynn McCleary

79. Varcarolis's Canadian Psychiatric Mental Health Nursing, Canadian 1st Edition: Margaret Jordan Halter

80. Understanding Global Cultures: Metaphorical Journeys Through 34 Nations, Clusters of Nations, Continents, and Diversity, 6th Edition: Martin J. Gannon & Rajnandini K. Pillai

81. Principles of Contract Law, 3d (Concise Hornbook Series): Robert Hillman

82. Understanding Motor Development: Infants, Children, Adolescents, Adults, 7th edition: David Gallahue & John Ozmun & Jacqueline Goodway

83. Maternal, Fetal, & Neonatal Physiology (Maternal Fetal and Neonatal Physiology), 4th Edition: Susan Blackburn

84. Japanese From Zero! 1: Proven Techniques to Learn Japanese for Students and Professionals: George Trombley

85. Making Sense of Mass Education: Gordon Tait

86. Starting Out with Java: From Control Structures through Objects, 6th Edition: Tony Gaddis

87. Grant's Dissector, 16th edition: Alan J. Detton

88. Principles of Information Systems, 13th Edition: Ralph Stair & George Reynolds

89. OAuth 2 in Action: Justin Richer & Antonio Sanso

90. Study Guide for Fundamentals of Nursing: Geralyn Ochs

91. Shelly Cashman Series Microsoft Office 365 & Access 2016: Comprehensive: Philip J. Pratt & Mary Z. Last

92. Mastering the Requirements Process: Getting Requirements Right, 3rd Edition: Suzanne Robertson & James Robertson

93. CISSP Guide to Security Essentials, 2nd Edition: Peter Gregory

94. Hacking Exposed Windows: Microsoft Windows Security Secrets and Solutions, 3rd Edition: Joel Scambray

95. Campbell Biologie: Gymnasiale Oberstufe (Pearson Studium - Biologie Schule) (German Edition): Neil A. Campbell & Jane B. Reece

96. Linux Hardening in Hostile Networks: Server Security from TLS to Tor (Pearson Open Source Software Development Series): Kyle Rankin

97. Fundamentals of Electric Circuits, 6th Edition: Charles Alexander

98. A History of Western Society Since 1300, Advanced Placement: John P. McKay & Bennett D. Hill & John Buckler & Clare Haru Crowston & Merry E. Wiesner-Hanks & Joe Perry

99. Ways of the World with Sources for AP*: Robert W. Strayer & Eric W. Nelson

100. The Earth and Its Peoples: A Global History, Volume I: To 1550, 6th Edition: Richard Bulliet & Pamela Crossley & Daniel Headrick & Steven Hirsch & Lyman Johnson

101. Voyages in World History, Volume 2, 3rd Edition: Valerie Hansen & Ken Curtis

102. Probability & Statistics for Engineers and Scientists with R: Michael Akritas

103. Crime, Victims and Justice: Essays on Principles and Practice: Marijke Malsch

104. Contemporary Business, Canadian Edition: Louis E. Boone & David L. Kurtz & Michael Khan & Brahm Canzer

105. Automation, Production Systems, and Computer-Integrated Manufacturing, 4th Edition: Mikell P. Groover

106. Accounting, 26th Edition: Carl S. Warren & James M. Reeve & Jonathan Duchac

107. Social Psychology, 9th Edition: Elliot Aronson & Timothy D Wilson & Samuel R. Sommers

108. Cracks in the Schoolyard—Confronting Latino Educational Inequality: Gilberto Q. Conchas

109. The Internet of Risky Things: Trusting the Devices That Surround Us: Sean Smith

110. Foundations of Business, 5th Edition: William M. Pride & Robert J. Hughes & Jack R. Kapoor

111. Effective Help Desk Specialist Skills: Darril Gibson

112. Social Psychology, 12th Edition: David Myers

113. Becoming a Critical Thinker: A User-Friendly Manual, 6th Edition: Sherry Diestler

114. Prioritization, Delegation, and Assignment - E-Book: Practice Excercises for the NCLEX Exam: Linda A. LaCharity & Candice K. Kumagai & Barbara Bartz

115. Qualitative Inquiry in Neoliberal Times (International Congress of Qualitative Inquiry Series): Unknown

116. The Official (ISC)2 Guide to the SSCP CBK, 4th Edition: Adam Gordon & Steven Hernandez

117. Fundamentals of Futures and Options Markets, 9th Edition: John C. Hull

118. Practice Makes Perfect: Advanced French Grammar: All You Need to Know For Better Communication (Practice Makes Perfect Series): Véronique Mazet

119. New Grade 9-1 GCSE Chemistry: AQA Revision Guide: CGP Books

120. New Grade 9-1 GCSE Biology: AQA Revision Guide: CGP Books

121. New Grade 9-1 GCSE Physics: AQA Revision Guide: CGP Books

122. Project Management For Dummies, 4th edition: Portny, Stanley E.

123. PMP Project Management Professional Review Guide, 3rd Edition: Kim Heldman

124. PMP® Certification All-in-One For Dummies®, 2nd Edition: Snyder, Cynthia

125. PMP® Exam Simplified: Updated for 2016 Exam (PMP® Exam Prep Series Book 4), 5th Edition: Aileen Ellis

126. The Complete ‘Ace Your PMP® Exam’ Series: Essential PMP® Concepts Simplified: Shiv Shenoy

127. Crack the New (2016) PMP® Exam in 4 Weeks: Using Simple, Proven, Step-by-Step Approach (Ace Your PMP® Exam): Shiv Shenoy

128. PMP Project Management Professional Study Guide, 4th Edition (Certification Press): Joseph Phillips

129. Public Policy: Politics, Analysis, and Alternatives, 5th Edition: Michael E. Kraft & Scott R. Furlong

130. Working With Challenging Parents of Students With Special Needs: Jean Cheng Gorman

131. Statistics in Practice, 1st Edition: David S. Moore & William I. Notz & Michael A. Fligner

132. Introduction to Programming with C++,International Edition, 3rd Edition: Y Daniel Liang

133. Focus on Personal Finance, 5th Edition: Les Dlabay & Robert J. Hughes & Jack Kapoor & Melissa Hart

134. Leviathan: Thomas Hobbes, Edwin Curley

135. Exploring Microsoft Word 2016 Comprehensive (Exploring for Office 2016 Series): Mary Anne Poatsy & Linda Lau & Lynn Hogan

136. Real World Psychology, 2nd Edition: Catherine A. Sanderson & Karen Huffman

137. Sociology: A Down-to-Earth Approach, 13th Edition: James M Henslin

[Daily Discussion] Sunday, January 13, 2019

Thread topics include, but are not limited to:

• General discussion related to the day's events
• Technical analysis, trading ideas & strategies
• Quick questions that do not warrant a separate post

Thread guidelines:

• Be excellent to each other.
• Do not make posts outside of the daily thread for the topics mentioned above.

Other ways to interact:

• Get an invite to live chat on our Slack group
• Set your flair to trade pretend money in the Flair Game
• Weekly threads: Newbie Mondays and Fundamentals Fridays

Please help me. Pokemon GO

Help me. When I joined my daughter at the event of Pokemon GO today, I inadvertently dropped the smartphone and broke it. My daughter is looking forward to getting Milotic at the next week's event, but I have no money to repair. If there are people who can cooperate please send BITCOIN to this address.

1Lma6tsZAFWeX3A8KFQdjF3UXeTrmArn4n

[Daily Discussion] Sunday, January 13, 2019

Thread topics include, but are not limited to:

• General discussion related to the day's events
• Technical analysis, trading ideas & strategies
• Quick questions that do not warrant a separate post

Thread guidelines:

• Be excellent to each other.
• Do not make posts outside of the daily thread for the topics mentioned above.

Other ways to interact:

• Get an invite to live chat on our Slack group
• Set your flair to trade pretend money in the Flair Game
• Weekly threads: Newbie Mondays and Fundamentals Fridays

The Blockchain Principles and their Potential

I was invited as speaker at a conference of European Education Experts which covered the topic “The New Student: Flexible Learning Paths and Future Learning Environments” (More Info)

I am not going to wrap-up this conference but give you a extract of my contribution to this conference. The topic of my speech was: “The Blockchain Principles and their Potential”.

I will start with two completely different perspectives about the relevance of this topic. The first perspective is a historic approach related to Vienna.

A distant view to the relevance of Blockchain

In the August 23rd 2018 edition of the Economist, an article about three Viennese exiles was titled with “Hayek, Popper and Schumpeter formulated a response to tyranny”. All three emphasised the relationship between liberty and economic progress. In their days, the threat to liberty and economic progress was the totalitarianism of the Nazis and other forms of fascism. Quote from the article “Hayek and Popper were friends but not close to Schumpeter. The men did not co-operate. Nonetheless a division of labour emerged. Popper sought to blow up the intellectual foundations of totalitarianism and explain how to think freely. Hayek set out to demonstrate that, to be safe, economic and political power must be diffuse. Schumpeter provided a new metaphor for describing the energy of a market economy: creative destruction.”

The ideas of these three exiles were still (or even more) relevant in the aftermath of the second world war, as both, capitalism and communism were not immune to the dangers of centralised authorities and it’s power of execution and control.

Today in the beginning of the 21st century, concern about centralisation and power are still appropriate. Digitisation and the internet have brought new forms of centralisation, hence power to those who control the internet. Not to forget the impact of social media on free thinking.

A close view: What is Blockchain?

I am a mathematician, and my approach to blockchain started with prime numbers and Euler’s theorem. This brings us, after the Vienna excursion to 20th century, to the 17th and 18th century. Without prime numbers, which is at the heart of cryptography, we would not talk about Blockchain at all today! So, I could claim to be a distinguished expert of blockchain technology although I am aware, there is more than only numbers relevant to understand a blockchain.

It took me a while to realize, that for the time being this picture of blind man, touching an elephant is a good metaphor for the discussions about blockchain. At conferences, experts like me talk to each other about their different experience of blockchain without having a complete picture of the artifact. And, sorry for this amplification, most of the audience listens with interest because they even hadn’t the opportunity to touch the object so far!

Possible Perspectives on Blockchain

Today, the predominant perspective on Blockchain is related to its financial impact. The first Blockchain implementation was indeed a pure financial instrument, called Bitcoin.

But there are other perspectives as well, still the technical perspective is very important, many questions how to build and run a blockchain infrastructure are not answered yet. Huge improvements in technology are still necessary to scale up a global and reliable blockchain infrastructure. With the inception of the second big blockchain project, Ethereum, a whole new field of business applications emerged. The idea of automated business transactions, named as smart contracts, is the source of new business models which have already started to fulfil Schumpeter’s principle of “creative destruction”.

Of course, when things start to change, objections and concerns are close. And this gives a huge field of activities for the legal and political cast. But also, legal services will be affected by blockchain based transactions.

The problem statement of Bitcoin’s founders

To understand the principles of Blockchains it is necessary to know what the initial vision behind the first blockchain was. In the autumn of 2008 when the crisis of the financial system became apparent, an anonymous author “Satoshi Nakamoto” made statements about several shortcomings of the financial system and proposed an alternative payment system called Bitcoin. The main issues Satoshi stressed on was trust, respectively lack of trust and privacy and identity theft. It is very important to understand, that the problem statement of Satoshi was related to the behaviour of centralised authorities.

Bitcoin makes a distinguished political statement

This is article from January 3rd 2009 (print media had a good time then) announcing another bailout of British banks is literally a cornerstone of Bitcoin. On February 11th 2009 the Bitcoin software and the blockchain were released and everybody was invited to participate.

The first block of the Bitcoin Blockchain contains a short text which is not relevant for the program but makes a reference to the article in the Times. This text is stored in the Bitcoin blockchain and is also part of the source code, because is the first block. This means: This message is stored on thousands of computers around the world, and the chances that it will not disappear as long as computers are operational on this planet are quite good.

Design Principles of Bitcoin

Bitcoin is a global system which uses mathematics and computer science to build an open source software which is deployed on a global distributed network. Rules and controls of the system are connected to human behaviour and economic principles and organized with algorithms and game theory. The main strength of Bitcoin lies in the combination of several different principles:

It is a global system, where everybody connected to the internet can participate.

It uses mathematics, game theory and computer science for its algorithm. This algorithm reflects the user behaviour and is steered by laws of random and economic incentives.

The main principles of a Blockchain Algorithm

Now, leaving Bitcoin and going to the more general principles of other blockchains, we still recognize the basic characteristics of Bitcoin. If you do not see a similarity to Bitcoin, then it is not a Blockchain! Blockchains check and perform transactions from any source and store them in a public database (also called public ledger) on all participating nodes. Transactions are signed and identified by a public key, the owner of the transaction is identified by a private key.

Secure Identities and transactions with:

Cryptography

Distributed multilayer consensus

Economic incentives

Randomized execution

The potential of Blockchains

Most people talking and thinking of Blockchain refer to a focused area of application without referring to the big picture of “how the world works”. Satoshi was complaining about the role of the banks (and I agree with him), but I don’t think that he was referring explicitly to our three exiles from Vienna: But still, we can categorize the impact or potential of blockchain in their terms.

Blockchains diffuse the role of centralized organizations and systems like banks, government, companies

Blockchains give the control over identity and data to the single user

Blockchains are a seed for new structures in communication and business processes

And this brings us back to the article in the Economist, which concludes, that today we should fight for a decentralisation of the internet, so that individuals own their own data and identities, because unless power is dispersed, it is always dangerous.

One example from my personal experience: Scientific publishing, a 25 billion $ market

I would like to give you one example, which is related to Education, Research and Publication. I am personally engaged in this project, called EUREKA, which seeks to change completely the process of scientific publishing. Today, when you have research results, you send your findings to a publisher which organizes the review and publication of your article. This process has besides many shortcomings the effect that the whole financial profit goes to global companies whereas the researchers who do the whole work get nothing and the bill is mostly paid by taxpayers through research funding. With EUREKA the ownership of intellectual contributions stays with its author, and the exchange of money is directly between the authors and their readers.

Blockchains are a challenge for everybody!

This following list of impacts of blockchain for individuals comes from the JRC Science for Policy Report in Education. Download report

Self-sovereignty, i.e. for users to identify themselves while at the same time maintaining control over the storage and management of their personal data;

Trust, i.e. for a technical infrastructure that gives people enough confidence in its operations to carry through with transactions such as payments or the issue of certificates;

Transparency & Provenance, i.e. for users to conduct transactions in knowledge that each party has the capacity to enter into that transaction;

Immutability, i.e. for records to be written and stored permanently, without the possibility of modification;

Disintermediation, i.e. the removal of the need for a central controlling authority to manage transactions or keep records;

Collaboration, i.e. the ability of parties to transact directly with each other without the need for mediating third parties.

I agree very much with each of these points. But we must consider, that unless everybody understands these things and starts to accept the consequences of change, it will not happen by itself. It is still a long way to go which will need also a lot of time. Although I am enthusiastic about Blockchains, I do not believe, that they are only for our good. They will change the internet and how we use it.

But please do not let experts and lobbyist alone shape how this is done, all of us are relevant in these decisions. Thank you for reading my article, I look forward to discussions with you.

Walter Dettling

I'm writing a series about blockchain tech and possible future security risks. This is the fourth part of the series explaining the special quality of going quantum resistant from genesis block.

In part 4 I describe the advantages of going quantum resistant from genesis block. Genesis block is the first block of a blockchain. Being quantum resistant from genesis block means that a project launches from the very first beginning while using a quantum resistant signature scheme. This has several advantages I like to discuss in this part of the series.

Part 1 here Part 2 here Part 3 here

Quantum resistance (QR) from genesis block. Why is it a special quality?

Content:

A (Posted here)

What are the challenges of upgrading an existing blockchain to a quantum resistant one?

What you see is what you get: the performance of other blockchains that upgrade later, could be different after the upgrade.

The whole architecture can be designed around post-quantum cryptography.

B (posting tomorrow)

Lost addresses and the human factor: a partly protected circulating supply after a quantum resistant upgrade

The time factor

The case of a black swan event where unexpectedly fast, an entity will appear to have a quantum computer of critical level.

The fourth part is divided into two sub parts: 4A and 4B due to the size of the content. This should be fun and readable so part 4B will follow tomorrow.

What are the challenges of upgrading an existing blockchain to a quantum resistant one?

If a special quality doesn’t solve a certain issue, it would be of no value, so let’s first dig a bit deeper in the future issues for current running blockchains. It is important to start with mentioning the simple fact that a launched, working blockchain isn’t something that can be adjusted with the flip of a switch. Upgrading a blockchain to a post-quantum signature scheme is no small undertaking. Changing a signature scheme is not just copy paste and change some lines of code. It’s actually a decent amount of coding that needs to be done.

We are not simply talking about a core framework upgrade. Rather, all aspects of the project will end up needing an upgrade. The supporting systems that allow the blockchain to operate will also need to be upgraded. Software wallets, hardware wallets, block explorers, mining operations, pools... anything connected to an API and more will also need a brush up of code to be compliant with the new changes. Then exchanges will also need to adapt to the new chain. And for example, for a blockchain like Bitcoin and Ethereum this is going to be extra complex, as they need to fully disable their old signature scheme.

The second challenge is that you need consensus, you need the majority of the nodes to upgrade. If you want to change the signature scheme and make sure the old, vulnerable scheme is rejected, you need to upgrade at least the majority of nodes, or you will end up with the old, vulnerable signature scheme or two different blockchains where the main chain will still be using the old signature scheme and thus will not be quantum resistant. As explained in the previous part, we can’t have the old signature scheme to be valid because that would mean that the blockchain would still allow the use of vulnerable old public and private keys and thus the old vulnerable signatures for transactions, so at least the majority of the nodes need to upgrade to make sure that blocks which are constructed using the old rules and thus the old vulnerable signature scheme, are rejected by the network. This will eventually result in a fully upgraded network which only accepts the new post quantum signature scheme in transactions. So, consensus is needed.

The past has proven that reaching consensus in a decentralized system as blockchain, is not a fast, fluent process. You need the nodes to update to your new version. The nodes have the choice to do so or refuse. That makes it, so to speak, a democratic system which makes any change a slow process. The past has proven that a simple change to improve speed and transaction costs couldn’t be realized because miners couldn’t agree on to which of the working solutions would be implemented. There are several solutions to a serious problem, but none is implemented (at least not in the original chain). If you compare this to changing a signature scheme, it’s not going to be any easier. There will be different schemes available, different choices to make how to implement them, and thus there will be different options on the table. The need for QR might be a huge incentive to implement as soon as possible, but that doesn’t mean there won’t be different interests for the people running nodes. One option might mean better performance, but 60% of the people running nodes, will need to buy new equipment. The other option might mean lesser investments for equipment, but also slower transactions and the risk of losing users and market share. These discussions and differences in interest and view point, will not help to reach consensus fast.

Another challenge is that post-quantum is a specialized kind of cryptography. Post-quantum cryptography is a real specialty. Choosing the right scheme and implementing it without the right knowledge, might backfire. So implementing post-quantum cryptography without consulting a post-quantum cryptographer and commissioning an external audit is a serious risk. What will you use? Will you use XMSS? How you make sure your blockchain can handle stateful signatures? You use WOTS+? How you make sure this is user-friendly? How will you make sure there is no old debtor who will sent funds to an old address? You use SPHINCS? How you going to handle 41KB signatures? You use BLISS B? How you prevent side channel attacks? You waiting for a NIST outcome? There is no guarantee that will be a magic scheme. Might still take a lot of work to implement.

Just an example: If you will use WOTS+, you will need to find a solution for the fact that you can't reuse addresses. The most well known example is IOTA. They had some unexpected issues where people actually lost money. The problem went a bit deeper than just not reusing addresses: http://blog.lekkertech.net/blog/2018/03/07/iota-signatures/ This is fixed from the user perspective in the Trinity wallet. The remaining issue to solve now is the fact that constantly changing addresses, excludes IOTA from being used by companies. Any company needs a standard address to pay to for the obvious reasons. (qr-code stickers meaning the quick response code not to be confused with the abbreviation for quantum resistance, invoicing and the random order of customers paying invoices, etc.) Propositions for a solution have been made so this is still an ongoing process for IOTA.

XMSS is even more complex to implement compared to WOTS+.

So it’s quite a time-consuming and challenging project to implement and upgrade an existing project. As an existing fully quantum resistant blockchain, having your security in check in advance, gives the certainty you’re in time, and all is checked, audited and working properly. Which obviously is a plus.

What you see is what you get: the performance of other blockchains that upgrade later, could be different after the upgrade.

The majority of NIST’s suggested post-quantum signature schemes will drastically increase the block size and take more resources to compute. This may in turn slow down the transactions per second a lot of projects aim to reduce. Quantum resistant signature schemes will mean bigger signatures. That has consequences for the performance of a blockchain, unless big innovative changes are made. So at the moment where quantum resistance becomes a must, something unexpected will happen. Projects that have postponed an implementation of quantum resistant signature schemes will be set back. The upgrade to a safer signature scheme will actually be partly a downgrade for pretty much all existing projects. There are only two blockchains who use quantum resistant signature schemes right now: QRL (XMSS) and Mochimo (WOTS+). The only reason for them to change signature schemes, is if a better, more efficient post-quantum signature scheme will be developed compared to the post-quantum signature scheme they use right now. NIST has initiated the research and review of post-quantum cryptography. https://www.nist.gov/news-events/news/2016/04/nist-kicks-effort-defend-encrypted-data-quantum-computer-threat So there might be something better available in the future. If this is indeed better, going from XMSS to something better, will be an over all upgrade. (NIST will either come up with something better, more efficient, or there will be nothing new to recommend at all). So while all other projects will partly downgrade performance wise, quantum resistant blockchains will either stay the same or upgrade and perform better.

How bigger signatures influence the speed with which transactions are sent and confirmed on a blockchain: first a quick summary of the way transactions are handled: All miners, collect all transactions that people are sending in a transaction pool. There, transactions wait until a miner puts a number of these collected transaction in a block. This is where a block is constructed. After he has constructed a block, he has to solve a hash puzzle applied on his list of transactions that he registered on his block. The miner who has solved his hash puzzle, is allowed to put his block on the network. If this block will eventually be part of the longest chain, the transaction will be confirmed and validated. Either the size of the block will be influenced by bigger signatures, or if the block size is fixed, the amount of transactions that fit in a block will be influenced.

Now there are two types of speed that are influenced and are both important for the performance of the blockchain:

• Capacity, so the amount of transactions a blockchain can confirm in a second at maximum capacity. So if BTC for example can confirm 7 transactions a second (it’s max capacity), then as soon as more than 7 transactions per second are added to the network, BTC has reached its maximum capacity. In that case, the individual transactions will need to wait in line and the individual transaction speed is slowed down. (Unless you increase your fee, then your transaction will be prioritized and you might make the standard individual transaction speed. Of course depending on the height of other fees.)
• Individual transaction speed. This is the time within which you send a transaction and your transaction is confirmed on the network. This is the speed that applies for the moment where the blockchain is operating under its maximum capacity. So that means a transaction is added to a block almost as soon as it arrives at a node and gets processed right away.

The capacity depends on the block time (the amount of time it takes for a block to be mined) and the amount of transactions that fit in a block. The bigger the signature, the bigger and “heavier” the transaction, which results in either fewer transactions fitting in one block or bigger block size. Which in turn then results in less transactions confirmed per block or bigger block times which both leads to less transactions per second.

Now there could be solutions for the big signature size issue. Solutions being developed right now for scaling, could solve the problem for quantum resistant blockchains. But this is ongoing research to be looked into more in depth.

To overcome the shortfalls of post-quantum signature schemes some developers may decide to roll their own crypto, which has majorly failed in the past with other projects. Cryptography is difficult to understand and implement, much less post-quantum cryptography. Besides that it has to be tested and checked, preferably by external, professional parties to be proven secure. To this end there are only a handful of researchers worldwide even qualified in this specialty field.

The whole architecture can be designed around post-quantum cryptography.

Besides the fact a blockchain is from the start designed around post-quantum signature schemes, one of the key points in the architecture would be a flexible signature space for addresses and having a chain that's already designed to handle, for example stateful signatures. The handling of stateful signatures would come naturally if the chain is already using a post-quantum scheme like that, but should another come along that's better, the whole architecture is build and ready to switch. This is compared to one that has a small signature space and can't define them, as well as the lack of capability of handling state in chain (for example Bitcoin).

Take QRL for example: https://docs.theqrl.org/developers/address/#descriptor QRL already implemented a quantum resistant signature scheme: XMSS. But at the same time their chain architecture is build to switch signature schemes: When you form a QRL address, First 3 bytes of your address forms the Descriptor. In Descriptor bit number 4 to 7 are used to specify signature scheme. These 4 bits are used to specify if we have any other signature scheme.

In part 4B I dive deeper in the issue of lost addresses for existing blockchains like for example the ~1 milion BTC in Satoshi's wallet. Also I will get into the time issue and a possible black swan event.

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