Question

Do the following with OpenSSL:

1. Create a 2048 bit RSA private key.
2. Convert this private key into a text format so it shows the following information:

• modulus
• public exponent (e)
• private exponent (d)
• the primes (p and q)

Use the appropriate command that generates this information and saves it in key.txt file.

3. Save the message "Hello from (your UID)" in a plaintext file message.txt. Using openssl's rsautl option to sign this message with your private key (key.txt). Save this signed message as the file signed.txt. Use this link for reference.
4. Using openssl's rsautl option encrypt the message.txt file using your private key generated in Step#1 above. Save the encrypted message as encrypted.txt.
5. Assemble all the files of key.txt, signed.txt, message.txt and encrypted.txt and all procedure screenshots of above work into a single file to upload for submission.

Answer 1

How do I generate an RSA key?
Use the genrsa option.

# default 1024-bit key, sent to standard output
openssl genrsa

# 2048-bit key, saved to file named mykey.pem
openssl genrsa -out mykey.pem 2048

# same as above, but encrypted with a passphrase
openssl genrsa -des3 -out mykey.pem 2048

How do I generate a public RSA key?
Use the rsa option to produce a public version of your private RSA key.

openssl rsa -in mykey.pem -pubout

openssl genrsa -out mykey.pem 1024
will actually produce a public - private key pair. The pair is stored in the generated mykey.pem file.

openssl rsa -in mykey.pem -pubout > mykey.pub
will extract the public key and print that out

To just output the public part of a private key:

openssl rsa -in key.pem -pubout -out pubkey.pem
To get a usable public key for SSH purposes, use ssh-keygen:

ssh-keygen -y -f key.pem > key.pub

RSA private key syntax

An RSA private key should be represented with the ASN.1 type
RSAPrivateKey:

RSAPrivateKey ::= SEQUENCE {
version Version,
modulus INTEGER, -- n
publicExponent INTEGER, -- e
privateExponent INTEGER, -- d
prime1 INTEGER, -- p
prime2 INTEGER, -- q
exponent1 INTEGER, -- d mod (p-1)
exponent2 INTEGER, -- d mod (q-1)
coefficient INTEGER, -- (inverse of q) mod p
otherPrimeInfos OtherPrimeInfos OPTIONAL
}