fix link to the CrypTool book

README.md

@@ -168,7 +168,7 @@ That seems somewhat out of scope, isn't it? But these are books only fully avail
 
 * [A Graduate Course in Applied Cryptography](https://crypto.stanford.edu/~dabo/cryptobook/) - By Dan Boneh and Victor Shoup. A well-balanced introductory course into cryptography, a bit of cryptanalysis and cryptography-related security.
 * [Analysis and design of cryptographic hash functions, MAC algorithms and block ciphers](https://web.archive.org/web/20220209130435/https://www.esat.kuleuven.be/cosic/publications/thesis-16.pdf) - Broad overview of design and cryptanalysis of various ciphers and hash functions, by Bart Van Rompay.
-* [CrypTool book](https://www.cryptool.org/en/ctp-documentation/ctbook) - Predominantly mathematically oriented information on learning, using and experimenting cryptographic procedures.
+* [CrypTool book](https://www.cryptool.org/en/ctbook/) - Predominantly mathematically oriented information on learning, using and experimenting cryptographic procedures.
 * [Handbook of Applied Cryptography](https://cacr.uwaterloo.ca/hac/) - By Alfred J. Menezes, Paul C. van Oorschot and Scott A. Vanstone. Good classical introduction into cryptography and ciphers.
 * [The joy of Cryptography](http://web.engr.oregonstate.edu/~rosulekm/crypto/) - By Mike Rosulek. A lot of basic stuff covered really well. No ECC.
 * [A Computational Introduction to Number Theory and Algebra](http://www.shoup.net/ntb/) - By Victor Shoup, excellent starters book on math universally used in cryptography.