This document discusses Bitcoin transaction malleability. It begins by providing background on Bitcoin currency and transactions. It then explains that transaction IDs in Bitcoin can change even if the transaction details remain the same, due to a property called transaction malleability. This can cause issues for applications that rely on the transaction ID alone. The document advises not relying solely on transaction IDs and not automatically reissuing transactions in the case of failures.

1. BITCOIN
TRANSACTION
MALLEABILITY
Daniel
Chechik
Senior
Security
Researcher

2. Bitcoin
Currency

3. Bitcoin
Currency

4. Bitcoin
Currency

5. Bitcoin
Currency

6. Bitcoin
Currency

7. Bitcoin
Currency

8. Bitcoin
in
Numbers

9. Bitcoin
in
Numbers

10. Mt.Gox
Money
Heist

11. Mt.Gox
Money
Heist
1st February
1st April

12. TRANSACTION
MALLEABILITY

13. P2P
LoFery

14. P2P
LoFery

15. P2P
LoFery
MessageID
(sha256)
From:
Lo5ery
Prize:
You
won
a
Car!
To:
“Lucky
Winner”
To:
Daniel
Length
…
Signature(DER)
Length
…
Bimba

16. P2P
LoFery

17. P2P
LoFery
MessageID
(sha256)
From:
Lo5ery
Prize:
You
won
a
Car!
To:
“Daniel”
Length
…
Signature(DER)
…
Length

18. P2P
LoFery
MessageID
(sha256)
From:
Lo5ery
Prize:
You
won
a
Car!
To:
“Daniel”
Length
…
Signature(DER)
…
Length
ID Signature SUPPLIED
f5d8ee... ABCD ✓

19. P2P
LoFery

20. P2P
LoFery
MessageID
(sha256)
From:
Lo5ery
Prize:
You
won
a
Car!
To:
“Daniel”
Length
Signature(DER)
…
Length
ID Signature SUPPLIED
f5d8ee... ABCD ✓
5e67s… ABCD û
…

21. P2P
LoFery

22. P2P
LoFery
ID Signature SUPPLIED
f5d8ee... ABCD ✓
5e67s… ABCD û
15c4a… GHJK ✓

23. P2P
LoFery

24. P2P
LoFery

25. Take
Away
§ Do
not
rely
on
a
TransacIon
ID
alone
for
transacIon
confirmaIon
§ Do
not
automaIcally
reissue
a
transacIon
in
case
of
failure

26. Take
Away

27. Daniel.chechik@gmail.com
@danielchechik
Thank
You!