Script for generating a public/private key pair

generate_keys.sh

#!/bin/bash

# Generate private key in PEM format
openssl genpkey -algorithm RSA -out private.key.pem -pkeyopt rsa_keygen_bits:2048

# Generate public key in PEM format (intermediate step)
openssl rsa -pubout -in private.key.pem -out public.key.pem

# Convert private key to JWK (JSON Web Key) format
private_jwk=$(openssl rsa -in private.key.pem -noout -text | \
    awk '
    /modulus:/{p=1;next}/publicExponent:/{p=0}p' | \
    tr -d ' \n:' | \
    xxd -r -p | base64 -w 0 | \
    tr '+/' '-_' | tr -d '=')

private_exp=$(openssl rsa -in private.key.pem -noout -text | \
    awk '/privateExponent:/{p=1;next}/prime1:/{p=0}p' | \
    tr -d ' \n:' | \
    xxd -r -p | base64 -w 0 | \
    tr '+/' '-_' | tr -d '=')

# Convert public key to JWK format
modulus=$(openssl rsa -pubin -in public.key.pem -modulus -noout | \
    cut -d'=' -f2 | \
    xxd -r -p | base64 -w 0 | \
    tr '+/' '-_' | tr -d '=')

# Generate key ID (kid)
kid=$(openssl rand -hex 32)

# Create public key JWK
echo "{
  \"kty\": \"RSA\",
  \"kid\": \"$kid\",
  \"n\": \"$modulus\",
  \"e\": \"AQAB\",
  \"alg\": \"RS256\",
  \"use\": \"sig\"
}" > public.key.json

# Create private key JWK
echo "{
  \"kty\": \"RSA\",
  \"kid\": \"$kid\",
  \"n\": \"$modulus\",
  \"e\": \"AQAB\",
  \"d\": \"$private_exp\",
  \"alg\": \"RS256\",
  \"use\": \"sig\"
}" > private.key.json

echo "Keys generated successfully!"
echo "Files created:"
echo "- private.key.pem (Private key in PEM format)"
echo "- private.key.json (Private key in JWK format)"
echo "- public.key.json (Public key in JWK format)"

# Display the generated kid for reference
echo -e "\nKey ID (kid) for reference:"
echo "$kid"