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Fixity

Name:

Fixity

Version:

0.5 (2011-03-30)

Status:

Alpha

Specification:

Merritt Fixity Service

Download:

Not available

More information:

Curation home page

In our development process for the Merritt repository, we first create a detailed specification for each micro-service and then develop software based upon the specification. Having a specification helps us think through issues and work out problems before we start to write code. It's always helpful to have people reviewing our specifications, to notice issues or implications we may have missed or not fully understood.

Fixity is a method to test for file integrity and corruption. The Fixity service will verify the bit-level integrity of files managed in the Merritt Repository with a two-part test: Is the filesize of each file unchanged? Is the message digest value of each file unchanged?

We note and store the filesize of each file as it is submitted to Merritt. Curators may also include a message digest value for their content during submission. If none is supplied, Merritt will automatically compute a SHA-256 digest during ingest processing.

Each iteration of the Fixity service will compare the stored filesize value with the file in its current state. The Fixity service will also recalculate the message digest and compare with the stored value. If either of these checks results in a discrepancy, Merritt staff will be notified, so they can take preservation action to restore the uncorrupted state of the file using replica copies.

Please read the draft specification, and let us know any thoughts you have in response. In particular, please consider these questions:

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