Reddit mentions of Introduction to Modern Cryptography (Chapman & Hall/CRC Cryptography and Network Security Series)

Specific to Cryptanalysis (in order):

1. start with this great tutorial on FEAL cryptanalysis
   
   
2. then try the matsano challenges
   
   
3. finally followed by Schneier's self study course on cryptanalysis.
   
   
   Good intermediate texts on cryptography/cryptology:
   
   
4. From a mathematical perspective: An Introduction to Mathematical Cryptography by Silverman et al.
   
   
5. From a provable security perspective (probably the most important to both academia and industry): Introduction to Modern Cryptography (new 2nd ed.) by Katz & Lindell
   
   
6. Serge Vaudenay's A Classical Introduction to Cryptography (it's an in between of the above 2 books).
   
   
7. Christoph Paar's Understanding Cryptography with a video course.
   
   
   Lastly, a really fantastic all around book on network security (including crypto) would be: Network Security 2nd Ed. by Kaufman and Perlman. It is a little old though but still relevant. Also has great analysis of real world protocols such as IPsec (IKE, ISAKMP), Kerberos, SSL/TLS, S/MIME, etc.

An accessible undergraduate textbook that I have used and enjoy is Introduction to Cryptography with Coding Theory. That being said, I have not looked at many others.

A much more technical (but formally correct) textbook is Introduction to Modern Cryptography by Katz and Lindell.

On a side note, cryptography is a very mathematical field. So take as many math courses as you can. Number theory and algebra in particular.

Yes, abstract algebra will be useful for some parts. So will number theory.

You should definitely have some idea about algorithms and time/space complexity.

An introductory book like Katz - Lindell will be pretty self contained and it will be easy to understand having a math degree.

I have no clue what you're talking about but if you want proof it's from this book:

https://www.amazon.com/Introduction-Cryptography-Chapman-Network-Security/dp/1466570261/ref=pd_lpo_sbs_14_t_1?_encoding=UTF8&psc=1&refRID=CP21V6HXBZP3C3SFEM5N