LibraryConsensus2014Design paperCorpus record
Proof of Stake: How I Learned to Love Weak Subjectivity
Weak Subjectivity. Vitalik Buterin.
A node that has been offline longer than a known window must take a recent checkpoint from a source it already trusts. Inside the window, the protocol can defend itself.
A reading of the public document. Not a copy of it, and not a claim about a later network that reused the name.
A wallet that syncs a proof-of-stake chain from genesis with no checkpoint has ignored the attack this note names.
- Evidence
- Primary paper
- Re-measured
- No
- Assumptions
- 3
- Records linked
- 4
Code
Source, repository, and what is actually hosted
- Ethereum blog, 2014https://blog.ethereum.org/2014/11/25/proof-stake-learned-love-weak-subjectivity
- The source URL is not a GitHub repository. No code remote is invented.
- Full text is not mirrored. Public availability is not a licence to copy the file onto this site.
- Add to a reading list
01 Claim ledger
What the paper is allowed to say
Each row is a sentence already in the study. The status is the same on every row: a model claim, not a live measurement.
Claim 01 · Paper model
The defect
A proof-of-stake chain can be rewritten from genesis by an attacker who buys long-dead keys, because those keys cost nothing to use once the stake is withdrawn.
Claim 02 · Paper model
The rule
A node that has been offline longer than a known window must take a recent checkpoint from a source it already trusts. Inside the window, the protocol can defend itself.
Claim 03 · Paper model
How it is put together
The checkpoint is not a new consensus algorithm. The window is a social and economic parameter. Long-range attacks are the reason the window exists.
Claim 04 · Paper model
Where the claim stops
Weak subjectivity is not trustlessness from genesis for a new node.
02 Three cuts
Observation, model, falsifier
A desk does not stop at the summary. Each claim is cut three ways, using only this study's own assumptions and checks. Nothing here is a new figure.
01 The defect
Observation
What the study says
A proof-of-stake chain can be rewritten from genesis by an attacker who buys long-dead keys, because those keys cost nothing to use once the stake is withdrawn.
Model
What has to hold
Weak subjectivity is not trustlessness from genesis for a new node.
Falsifier
What would retire it
What stake-withdrawal rule makes old keys useless inside the window?
02 The rule
Observation
What the study says
A node that has been offline longer than a known window must take a recent checkpoint from a source it already trusts. Inside the window, the protocol can defend itself.
Model
What has to hold
It is not a claim that checkpoints are incorruptible.
Falsifier
What would retire it
What stake-withdrawal rule makes old keys useless inside the window?
03 How it is put together
Observation
What the study says
The checkpoint is not a new consensus algorithm. The window is a social and economic parameter. Long-range attacks are the reason the window exists.
Falsifier
What would retire it
Where does a new node get the checkpoint?
04 Where the claim stops
Observation
What the study says
Weak subjectivity is not trustlessness from genesis for a new node.
Model
What has to hold
Weak subjectivity is not trustlessness from genesis for a new node.
Falsifier
What would retire it
How long is the weak-subjectivity period?
03 Sequence
One action, as an operating tape
- 01Stay online, or sync often enough to stay inside the window.
- 02If you were gone too long, obtain a state from a client, a friend, or a checkpoint list.
- 03Then follow the fork-choice rule from that state.
- 04How long is the weak-subjectivity period?
04 Load-bearing
The argument, and where a pitch drops it
Why it is still on the desk
The cut
A wallet that syncs a proof-of-stake chain from genesis with no checkpoint has ignored the attack this note names.
Why it carries weight
If this cut is skipped, the paper's name is being used without the mechanism that makes the name mean anything.
Where it is dropped
Weak subjectivity is not trustlessness from genesis for a new node.
After the text
The cut
Ethereum's later consensus uses weak-subjectivity checkpoints in practice. The note is the argument, not the client.
Why it carries weight
If this cut is skipped, the paper's name is being used without the mechanism that makes the name mean anything.
Where it is dropped
05 Register
What has to be true
06 Divergence
What happened after the paper
Ethereum's later consensus uses weak-subjectivity checkpoints in practice. The note is the argument, not the client.
A later client, parameter set, or reward formula is a different object. Cite this paper for the mechanism. Cite a primary release for the network. This desk has not re-run the proof.
07 Pre-mortem
What to check before you use the idea
- 0 of 3 marked on this browser. A mark is a reading note, not a pass, a rating, or a recommendation.
08 Anatomy
The paper, in the order a builder needs
The problem it names
A proof-of-stake chain can be rewritten from genesis by an attacker who buys long-dead keys, because those keys cost nothing to use once the stake is withdrawn.
What the design proposes
- The checkpoint is not a new consensus algorithm.
- The window is a social and economic parameter.
- Long-range attacks are the reason the window exists.
How the mechanism is specified
- Stay online, or sync often enough to stay inside the window.
- If you were gone too long, obtain a state from a client, a friend, or a checkpoint list.
- Then follow the fork-choice rule from that state.
What this page does not treat as proven
Why the desk still reads it
A wallet that syncs a proof-of-stake chain from genesis with no checkpoint has ignored the attack this note names.
09 Lexicon
Terms, opened into the record
- Long-range attack
- Rewriting history with keys that are no longer bonded.
- Checkpoint
- A recent state a returning node agrees to start from.
10 Repository
Every linked record on this page
Underlined words open a page that already exists: a concept, a protocol profile, a failure record, or another paper. If a word is not underlined, this desk does not have a record for it.
Concepts
Protocols
This is Blockchain Lab's reading of a public design paper. It is not the paper, not a copy of it, and not an offer of tokens, equity, custody or a partnership. Later network behaviour can diverge from the text. Nothing here is investment, legal or technical advice.
Research status: Design paper. Last reviewed: 1 October 2026. This is a reading of a public paper, not investment, legal or security advice.