In the world of encryption, what are the emerging trends and challenges, and how are they addressed with advanced solutions?

Comparing public-key encryption to symmetric encryption, what are some of the advantages and disadvantages of utilizing public-key encryption?

Is it feasible to encrypt data at both the connection and end-to-end levels? What is the advantage of this? Provide an example of a situation in which all forms of encryption are advantageous.

How do cryptographic techniques such as encryption, digital signatures, and hash functions contribute to the security of computer systems and networks? What are some of the key considerations that must be taken into account when designing and implementing cryptographic protocols for different applications and environments?