Added an abstract for ECDSAcerticom

Biblio.bib

@@ -55,13 +55,14 @@ @book{ASICSmithMJS
 }
 
 @misc{ECDSAcerticom,
-	url = "http://cs.ucsb.edu/~koc/ccs130h/notes/ecdsa-cert.pdf",
-	note = "Accessed 21 September 2017, \url{https://web.archive.org/web/20170921160141/http://cs.ucsb.edu/~koc/ccs130h/notes/ecdsa-cert.pdf}. Refer to section 6.2 for ECDSAPUBKEY, and section 7 for ECDSASIGN and ECDSARECOVER.",
+	url = "https://web.archive.org/web/20170921160141/http://cs.ucsb.edu/~koc/ccs130h/notes/ecdsa-cert.pdf",
+	note = "Accessed 21 September 2017, but the original link was inaccessible on 19 October 2017. Refer to section 6.2 for ECDSAPUBKEY, and section 7 for ECDSASIGN and ECDSARECOVER.",
 	title = {{The Elliptic Curve Digital Signature Algorithm (ECDSA)}},
 	publisher = {{Certicom Research}},
 	location = "Canada",
 	author = "Don Johnson and Alfred Menezes and Scott Vanstone",
 	year = "2001",
+	abstract = "The Elliptic Curve Digital Signature Algorithm (ECDSA) is the elliptic curve analogue of the Digital Signature Algorithm (DSA). It was accepted in 1999 as an ANSI standard, and was accepted in 2000 as IEEE and NIST standards. It was also accepted in 1998 as an ISO standard, and is under consideration for inclusion in some other ISO standards. Unlike the ordinary discrete logarithm problem and the integer factorization problem, no subexponential-time algorithm is known for the elliptic curve discrete logarithm problem. For this reason, the strength-per-key-bit is substantially greater in an algorithm that uses elliptic curves. This paper describes the ANSI X9.62 ECDSA, and discusses related security, implementation, and interoperability issues."
 }
 
 @misc{npmElectrum2017,