ContentDigest
off
This directive enables the generation of
Content-MD5
headers as defined in RFC1864 respectively
RFC2068.
MD5 is an algorithm for computing a "message digest" (sometimes called "fingerprint") of arbitrary-length data, with a high degree of confidence that any alterations in the data will be reflected in alterations in the message digest.
The Content-MD5
header provides an end-to-end
message integrity check (MIC) of the entity-body. A proxy or client
may check this header for detecting accidental modification of the
entity-body in transit. Example header:
Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==
Note that this can cause performance problems on your server since the message digest is computed on every request (the values are not cached).
Content-MD5
is only sent for documents served by
the core, and not by any module. For example, SSI documents, output
from CGI scripts, and byte range responses do not have this
header.