Salt in caching service is represented as String even it contains binary data

[pavel-jares-bcm]

This issue is based on #4408.

The Caching service generate salt to create a hash to store data in non-readable form. The salt is 16 random bytes. The issue is that the value is represented as String. So if the random bytes contains a control characters the created string doesn't have length 16 but less.

The correct behaviour should be to not translate the cache to String and the only one place we need it (stored value in the cache) use a different form, for example base64.