...

Fedora supports two types of fixity operations: Transmission fixity and persistence fixity.

Note: the information in this document applies to both internal and external content binaries.

Supported Digests

For these operations, Fedora supports the following digest algorithms:

...

Digests provided in this manner will be stored as metadata in Fedora, and can be found under the <http://www.loc.gov/premis/rdf/v1#hasMessageDigest> predicate when requesting the fcr:metadata resource for that binary.

The following example demonstrates transmission fixity Example: Creating a binary with a valid SHA1 digest:

# Create the binary with a SHA1
echo "test content" |
curl -XPUT http://localhost:8080/rest/binary_with_sha1 --data-binary @- -H "Digest: sha=4fe2b8dd12cd9cd6a413ea960cd8c09c25f19527"

# HTTP/1.1 201 Created

# Retrieve metadata for the binary
curl -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/binary_with_sha1

# <http://localhost:8080/rest/binary_with_sha1>
#     ...
#      premis:hasMessageDigest <urn:sha1:4fe2b8dd12cd9cd6a413ea960cd8c09c25f19527> ;

And the same example with With an invalid SHA1:

# Create the binary with a SHA1
echo "test content" |
curl -XPUT http://localhost:8080/rest/binary_with_sha1 --data-binary @- -H "Digest: sha=003d0450f6f7e6db635a04d23245b68e13365463" -v

# HTTP/1.1 409 Conflict
# Checksum mismatch, computed SHA digest 4fe2b8dd12cd9cd6a413ea960cd8c09c25f19527 did not match expected value 003d0450f6f7e6db635a04d23245b68e13365463

To provide more than one digest, comma separate the digests:With multiple digests

echo "test content" |
curl -XPUT http://localhost:8080/rest/binary_with_sha1 --data-binary @- -H "Digest: sha=003d0450f6f7e6db635a04d23245b68e13365463, md5=d6eb32081c822ed572b70567826d9d9d"

...

Users can perform a HEAD or GET request on a binary resource and include, as part of the request, a "Want-Digest" header, indicating that the server should recalculate the message digest per the provided algorithm and return the calculated digest as part of the response headers.  In this way, the client can compare the calculated value with the stored value to determine the integrity of the on-disk stored content.  A mismatch suggests some form of binary corruption and the repository manager should investigate and take appropriate actions to remediate.

See RESTful HTTP API - Fixity for usage.

Example: Requesting multiple digests

curl -I -H "Want-Digest: sha-256, sha-512/256" "http://localhost:8080/rest/binary_with_sha1"

# Digest: sha-512/256=00042c9c081986a401e25a1576b9aaa3c83d215a8efa180a73778203e3b4a678,sha-256=a1fff0ffefb9eace7230c24e50731f0a91c62f9cefdfe77121c2f607125dffae

On-demand Fixity Check

An on-demand fixity check can be requested by making a GET request to the /fcr:fixity endpoint of a binary. This will recalculate the digests of each algorithm that is on record for the binary, and compare against those stored digests. The results of the check will be returned in an RDF serialization. See RESTful HTTP API - Fixity for usage.

...

By default, Fedora will calculate and store a SHA-512 digest for all binaries if none were provided via "Digest" header. This digest will be available via the fcr:metadata endpoint for the binary, stored under a <http://www.loc.gov/premis/rdf/v1#hasMessageDigest> property.

...

# Create a binary without providing a digest
echo "test content" |
curl -XPUT http://localhost:8080/rest/binary_with_default --data-binary @-

# Retrieve the binary's metadata
curl http://localhost:8080/rest/binary_with_default/fcr:metadata

# <http://localhost:8080/rest/binary_with_default>
#         ...
#         premis:hasSize           "13"^^<http://www.w3.org/2001/XMLSchema#long> ;
#         premis:hasMessageDigest  <urn:sha-512:b22137a0e8969282b85e3f9375448307d14c5aabf41be66c4f6a0323bd03a3935972021e4c34aa30914e37b03c22594fe180eea9790e9ff147016c9dfae39d5a> ;
#         fedora:hasFixityService  <http://localhost:8080/rest/binary_with_default/fcr:fixity> .