Use new ssh key encryption EdDSA (type ed25519). Everything on using SSH agent. Not a script to run but a reference list of useful sample commands.

ssh-key-gen.sh

# Generating new SSH key best practice
# RSA is most widely used, 4096 bits recommended!
# Ed25519 was introduced in OpenSSH 6.5 of January 2014

# Ref: https://goteleport.com/blog/comparing-ssh-keys/
# Ref: https://medium.com/risan/upgrade-your-ssh-key-to-ed25519-c6e8d60d3c54

# List all your keys
for key in ~/.ssh/id_*; do ssh-keygen -l -f "${key}"; done | uniq

# Generate yours
# -a: It’s the numbers of KDF (Key Derivation Function) rounds. 
#   Higher numbers result in slower passphrase verification, increasing 
#   the resistance to brute-force password cracking should the private-key be stolen.
ssh-keygen -o -a 100 -t ed25519 -f ~/.ssh/id_ed25519 -C "[email protected]"

# Changing the private key's passphrase without changing the key
# This can also be used to change the password encoding format to the new standard.
ssh-keygen -f ~/.ssh/id_ed25519 -p

# Check the fingerprint
ssh-keygen -lf ~/.ssh/id_ed25519.pub
# Output:
# 256 SHA256:sMs42wBNIz4jeeNiCD/QNvGt966Lk8tI1oGMGwineth MacMladen @Buk5 (ED25519)
ssh-keygen -E md5 -lf  ~/.ssh/id_ed25519.pub
# Output:
# 256 MD5:c5:2e:3f:42:5d:63:74:87:97:a7:b6:c9:db:e4:fe:1a MacMladen @Buk5 (ED25519)

# Add your newly generated Ed25519 key to SSH agent:
ssh-add ~/.ssh/id_ed25519

# Adding keys under the default .ssh directory
# Add base keys
ssh-add
# If you want to add all of the available keys under the default .ssh directory
grep -slR "PRIVATE" ~/.ssh/ | xargs ssh-add

# List all active keys
# -l list keys fingerprints
# -L list actual keys
ssh-add -l

# Also by your ~/.ssh/config file:
# # Global SSH configurations here will be applied to all hosts
# IdentityFile ~/.ssh/id_dsa
# IdentityFile ~/.ssh/id_project1
# IdentityFile ~/.ssh/id_someotherkey

# To load the keys automatically and store the passphrases in the Keychain, 
# you need to configure your ~/.ssh/config file:

#Host *
#  AddKeysToAgent yes
#  UseKeychain yes
#  IdentityFile ~/.ssh/id_ed25519
#  IdentityFile ~/.ssh/id_rsa # Keep any old key files if you want

# Adding the private-key to the SSH agent and
# store the passphrases in the Keychain for authenticated use
ssh-add -K ~/.ssh/id_ed25519

# Specifying Specific Key to SSH into a Remote Server
ssh -i ~/.ssh/id_ed25519 [email protected]

# Check SSH connection ability
ssh -T [email protected]
ssh -T [email protected]
# Debug connection issues
ssh -v [email protected]

# Copying of the key to server
ssh-copy-id [email protected]
ssh-copy-id -i ~/.ssh/id_ed25519.pub -p 221 [email protected]