[tz] Bulletin C number 57

[Brian Inglis]

On 2019-01-19 15:54, Paul Eggert wrote:
> Hal Murray wrote:
>> Worked OK for ntpsec.
>>
>> There is a checksum in the file, but it only covers the non-comment digits in
>> the file.  (so white space changes are OK)
> 
> Good to know. So any problems should be limited to programs that try to parse
> the comments (such as the program in tzcode itself).

The NTP leap seconds file SHA1 check programs from IERS, Meinberg, or NIST hash
all the digit characters not after a comment character, plus the update and
expiry NTP times in the special comments lines, per the spec:

"Although the program uses the standard algorithm specified in FIPS 180-1, the
algorithm is applied only to a portion of the leap second file. Specifically:
1. comment lines, which start with # are not included when a comment signal is
read, the comment begins at that point and continues to the end of the line
2. white space characters in non-comment lines are not included
3. the numerical values (but not the white space) in the two special lines #$
and #@ are included."

and compares the result to the hex contents of the hash comment line.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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