How to decrypt a '.enc' file that has been encrypted with RSA using a public key?
openssl rsa -pubin -inform PEM -text -noout &lt; public_key.pem
Public-Key: (64 bit)
Modulus: 16513720463601767803 (0xe52c8544a915157b)
Exponent: 65537 (0x10001)


The modulus is small enough that you can easily factor it

After finding the prime factors, you can calculate the private exponent

After you have the private exponent, you raise each 64-bit block of ciphertext to the private exponent mod the modulus.