os_hash_algo.rst

Secure Hash Algorithm Support (Multihash)

The Secure Hash Algorithm feature supplements the current ‘checksum’ image property with a self-describing secure hash.

The self-description consists of two new image properties:

os_hash_algo

Contains the name of the secure hash algorithm used to generate the value on the image

os_hash_value

The hexdigest computed by applying the secure hash algorithm named in the os_hash_algo property to the image data

Hash Algorithm Configuration

os_hash_algo will be populated by the value of the configuration option hashing_algorithm in the glance.conf file. The os_hash_value value will be populated by the hexdigest computed when the algorithm is applied to the uploaded or imported image data.

These are read-only image properties and are not user-modifiable.

The default secure hash algorithm is SHA-512. It should be suitable for most applications.

The multihash is computed only for new images. There is no provision for computing the multihash for existing images.