Miscellaneous

Notarization

Definitions

  • A Hash H is a one-way function calculating a checksum on any data with the guarantee that no two inputs return the some output
  • A Notarization is the act of storing a hash on Blockchain as a proof of the existence of data at the point in time of the transaction T
  • A Signer S is the owner of public private key pair enabling to create and sign a transaction T on Blockchain
  • An Identity I is given to any entity by the public key for which it controls the private key.
  • An Attestation of the Identity of party P is the publication of the public key PK and further data such as name on Blockchain.
  • Key derivation is a mechanism to derive new public private key pairs from one seed.

Simple Notarization

Hashes H1..n ares calculated by parties P1..j and sent to service provider which creates and signs transaction T1..n with hash as payload. The service provider controls the private key PK1 controlled by service provider.

AdvantagesDrawbacks
Serves the basic purpose of notarizationEasy to fake data — every party can send faked data of other parties
Simple to use

Transparent Notarization with Identity

The Identity of party P with public key PK is attested on Blockchain. Party P calculates Hashes H1..n of data sets D1..n and notarizes each in a transaction with public key PK.

AdvantagesDrawbacks
Serves the basic purpose of notarizationNotarizations can be clearly linked to a party
The signer of a notarization is linked to the attestation via the public keyInformation on the number and timings of notarizations become transparent for each market participant

Blinded Notarization with Unverifiable Identity

The Identity of party P with public key PK is attested on Blockchain. Party P calculates Hashes H1..n of data sets D1..n. For each transaction a new public private key pair Pi created by key derivation is used.

AdvantagesDrawbacks
Serves the basic purpose of notarizationIdentity of signer cannot be verified - neither manually nor automatically
Transactions cannot be linked back to signer
No third party can observe the transaction history
Signer can prove ownership of keys used for signing a transaction

Blinded Notarization with Verifiable identity

The Identity of party P with public key PK is attested on Blockchain. Party P calculates Hashes H1..n of data sets D1..n. For each hash Hi a signature Si with the private key of PK is created. Both Hi and Si are stored in a transaction for which a new public private key pair Pi is created by key derivation.

AdvantagesDisadvantages
Serves the basic purpose of notarizationVerification of signature requires information about the signers identity, which could typically require the hashed data itself
Transaction cannot be linked back to signer
Signer of a transaction can be validated by verifying the signature with the attested public key
No third party can learn about the identity of a transaction signer without additional knowledge about the transaction signer, e.g. the name of the party
Signer can prove ownership of keys used for signing a transaction
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