doc: Remove links to further reading from pgcrypto docs

The pgcrypto docs contained a set of links for useful reading and
technical references. These sets of links were however not actively
curated and had stale content and dead links. Rather than investing
time into maintining these, this removes them altogether since there
are lots of resources online which are actively maintained.

Backpatch to all supported versions since these links have been in
the docs for a long time.

Reported-by: Hanefi Onaldi 
Reviewed-by: Magnus Hagander 
Reviewed-by: Tom Lane 
Discussion: https://postgr.es/m/170774255387.3279713.2822272755998870925@wrigleys.postgresql.org
Backpatch-through: v12

diff --git a/doc/src/sgml/pgcrypto.sgml b/doc/src/sgml/pgcrypto.sgml
index b108511b4244158cc168f00282ec126d8d9c2dfb..ba1f7e28508389684d64f5a09d3f49bc61ebabd8 100644 (file)
--- a/doc/src/sgml/pgcrypto.sgml
+++ b/doc/src/sgml/pgcrypto.sgml
@@ -1298,72 +1298,6 @@ gen_random_uuid() returns uuid
     ciphertexts of a given size.
    
   
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-   Useful Reading
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-     The GNU Privacy Handbook.
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-     Describes the crypt-blowfish algorithm.
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-      
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-     How to choose a good password.
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-     Interesting idea for picking passwords.
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-      
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-     Describes good and bad cryptography.
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-   Technical References
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-     OpenPGP message format.
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-     The MD5 Message-Digest Algorithm.
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-     HMAC: Keyed-Hashing for Message Authentication.
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-     Comparison of crypt-des, crypt-md5 and bcrypt algorithms.
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-     Description of Fortuna CSPRNG.
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-     Jean-Luc Cooke Fortuna-based /dev/random driver for Linux.
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