Fix URL links to \cite{BBDP2001} and \cite{BDJR2000}.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

protocol/protocol.tex

@@ -14511,6 +14511,7 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 } %nufive
     \item Fix a reference to nonexistent version 2019.0-beta-40 of this specification
           (in \crossref{diffadjustment}) that should be \historyref{2019.0.0}.
+    \item Fix URL links to \cite{BBDP2001} and \cite{BDJR2000}.
     \item Improve \texttt{protocol/links\_and\_dests.py} to eliminate false positives
           when checking DOI links.
 \end{itemize}

protocol/zcash.bib

@@ -600,7 +600,7 @@ Received August~3, 2015.}
    pages={362--399},
    date={2000-12},
    publisher={Academic Press},
-   doi={https://doi.org/10.1006/jcss.1999.1694},
+   doi={10.1006/jcss.1999.1694},
    url={https://cseweb.ucsd.edu/~mihir/papers/cbc.pdf},
    urldate={2021-03-08},
    addendum={Updated September~12, 2001.}
@@ -1583,8 +1583,8 @@ generic composition paradigm},
    addendum={Full version.},
    month={09},
    year={2001},
-   url={https://cseweb.ucsd.edu/~mihir/papers/anonenc.html},
-   urldate={2016-08-14}
+   url={https://cseweb.ucsd.edu/~mihir/papers/anonenc.pdf},
+   urldate={2021-09-01}
 }
 
 @book{LG2004,
@@ -1762,8 +1762,8 @@ Proceedings of the 10th IMA International Conference
    title={A {C}oncrete {S}ecurity {T}reatment of {S}ymmetric {E}ncryption:
 {A}nalysis of the {DES} {M}odes of {O}peration},
    date={2000-09},
-   url={https://cseweb.ucsd.edu/~mihir/papers/sym-enc.html},
-   urldate={2018-02-07},
+   url={https://cseweb.ucsd.edu/~mihir/papers/sym-enc.pdf},
+   urldate={2021-09-01},
    addendum={An extended abstract appeared in
 \textsl{Proceedings of the 38th Annual Symposium on Foundations of Computer Science
 (Miami Beach, Florida, USA, October 20--22, 1997)}, pages 394--403;
@@ -1880,7 +1880,7 @@ Proceedings of the 19th Annual International Cryptology Conference
    publisher={Springer},
    isbn={978-3-540-66347-8},
    doi={10.1007/3-540-48405-1_35},
-   url={https://link.springer.com/content/pdf/10.1007/3-540-48405-1_35.pdf}, % not paywalled
+   url={https://link.springer.com/content/pdf/10.1007/3-540-48405-1_35.pdf}, % full text
    urldate={2018-06-05}
 }