Title page 1

Contents 1

Abstract 2

1. Introduction 3

2. Assessment Approach 3

3.0. Quantum Computing 5

3.1. What is the "Quantum Threat"? 7

3.2. Post-Quantum Cryptography Timeline 8

4.0. Case Study: "Harvest Now Decrypt Later" Data Privacy Threat for Bitcoin 10

4.1. The Bitcoin Network 11

4.2. Traditional Cryptography usage in the Bitcoin Network 11

4.3. HNDL Risks for Bitcoin's Distributed Ledger Networks 14

4.4. HNDL Mitigations and Limitations 17

5. Conclusion 19

References 20

Figures 10

Figure 1. The HNDL threat began at the inception of Shor's algorithm in 1994 and remains ongoing. Data on the blockchain from 2009 onward is subject to the HNDL... 10

Figure 2. Illustrative order of obtaining a local replica of the Bitcoin ledger as a full node operator 12

Figure 3. Depiction of the nested relationship between cryptographic algorithms, cryptographic hash functions, and encoding schemes used to create a Bitcoin address 14