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1. CN attribute shall be a combination of the SAML attribute "displayName" and the eduPersonUniqueID
   1. If eduPersonUniqueID is not released eduPersonPrincipalName shall be used
   2. if eduPersonPrincipalName  is not released eduPersonTargetedID shall be used
2. The CA must ensure that the CN is unique within their namespace

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1. The RFC (5280 or 2459 to check) limits the length of the CN field to 64 characters. The string obtained as a combination of displayName+eduPUID may be longer than the limit. The CA must therefore re-hash the eduPUID to use a shorter, but globally unique, version of the user unique identifier.
   1. The re-hashing makes impossible for the e-infrastructure to map univocally the user's UID provided by the IdP to the certificate DN. This information can be provided by the CA as part of an incident response procedure.
   2. The CA must publish publicly the re-hashing algorithm, any change to the algorithm should follow a clear procedure to communicate the changes to all stakeholders. In this way the e-infrastructure can calculate the re-hashed user eduPUID used in the certificate and store the information internally, for a quicker incident response procedure.

References

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