FOLLOW THE MECHANISM
- 1Instruction
A wallet prepares the exact message.
- 2Signature
The secret key authorizes that message.
- 3Verification
Nodes check the signature and all other transaction rules.
A conceptual sequence. Real implementations can add steps, intermediaries, and conditions.
Authorization without revealing the secret
A signature scheme has a secret signing key and a related public verification key. The signer produces a signature over a specified message; anyone with the verification information can check it. Changing the signed message invalidates that signature. This is different from encrypting a message: a valid signature can accompany completely public data. Blockchain transactions use signatures to prove authorization under the applicable spending rules.
The message is the boundary
A wallet must know exactly what it is signing. A payment, a token-spending approval and an authentication message are different instructions even when they appear in a similar pop-up. Systems may include a chain identifier, nonce or domain separator to limit where an authorization is usable. A signature cannot compensate for misleading presentation: correctly signing an unintended instruction may still authorize the wrong action.
What the verifier does not learn
Verification establishes a relationship between a message and a key. It does not establish the signer’s legal identity, informed consent or honesty. A stolen key can produce signatures that are cryptographically indistinguishable from the legitimate holder’s signatures. The network can enforce rules about authorization, available funds and execution; it cannot read a person’s intention or decide whether an apparent gift was a scam.
A signature is only one check
A signed transaction can still be rejected because its inputs were already spent, its account balance is insufficient, its nonce is wrong or its contract call violates a condition. Nodes verify these additional rules before accepting a state change. Inclusion and finality come later. Separating authorization, validity and settlement makes it easier to understand why “signed” never means “the recipient has irreversibly received the funds.”
MAKE IT CONCRETE
An instruction with the wrong recipient
Imagine a valid signature over “pay address B 10 example units.” If the person intended address A, cryptography has not failed: it has faithfully authenticated the wrong instruction. Replacing B with A afterwards breaks that signature. This is why transaction content and wallet display belong in the security model alongside the mathematics.
FAILURE PATHS & COMMON MISREADINGS
Where the model can break
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