Did you already endorse someone at LinkedIn? For instance, someone claims that he knows C++ and you endorse this claim because you know it’s true. A large number of processes can be modelled in this way.
- skill endorsement in a business network
- existence of documents (see the Luxembourg Exchange Usecase)
- identity information (see ShoCard, uPort)
- memberships
- access rights
- …
A simple Solidity contract for managing claims and endorsements could look like below.
contract ClaimAndEndorse {
struct ENDORSEMENT {
uint creationTime;
}
struct CLAIM {
uint creationTime;
uint claimHash;
mapping (address => ENDORSEMENT) endorsements;
}
mapping (address =>
mapping (uint /* CLAIM GUID */ => CLAIM)) claims;
function setClaim(uint claimGuid, uint claimHash) {
CLAIM c = claims[msg.sender][claimGuid];
if(c.claimHash > 0) throw; // unset first!
c.creationTime = now;
c.claimHash = claimHash;
}
function unsetClaim(uint claimGuid) {
delete claims[msg.sender][claimGuid];
}
function setEndorsement(
address claimer, uint claimGuid, uint expectedClaimHash
) {
CLAIM c = claims[claimer][claimGuid];
if(c.claimHash != expectedClaimHash) throw;
ENDORSEMENT e = c.endorsements[msg.sender];
e.creationTime = now;
}
function unsetEndorsement(address claimer, uint claimGuid) {
delete claims[claimer][claimGuid]
.endorsements[msg.sender];
}
function checkClaim(
address claimer, uint claimGuid, uint expectedClaimHash
) constant returns (bool) {
return claims[claimer][claimGuid].claimHash
== expectedClaimHash;
}
function checkEndorsement(
address claimer, uint claimGuid, address endorsedBy
) constant returns (bool) {
return claims[claimer][claimGuid]
.endorsements[endorsedBy].creationTime > 0;
}
}
The fantastic thing about this very simple contract is that we now can answer the following question:
Who claims what and who endorses it?
...
Read the full article at blockchainers.org.
- Image from http://www.picserver.org/e/endorse.html
Great article and very informative! 👍
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