$ openssl aes-128-cbc -nopad -e -in in.txt -out out.txt \ Note that I've additionally used the -nopad option in the encryption because otherwise openssl adds an additional empty 16 bytes block to pad the input to the next 16 byte boundary. 32 byte hex into 16 byte binary data: $ perl -e 'print pack(q,q)' > in.txt But, you probably have put the hexadecimal data ( f34481ec3cc627bacd5dc3fb08f273e6) into the input file and thus created an input file consisting of 32 ASCII characters instead of 16 (binary) bytes.įirst decode the hex string into binary, i.e. The input and output files should contain the binary data while the IV and KEY arguments should be hexadecimal data. How can I view the output in the format provided in the AESAVS document? Is the method that I have applied for encrypting the plaintext file correct or am I missing something here? I also tried an online tool to verify the result provided in the online document, which also gives the correct output.
I am assuming that it is being encrypted correctly because when I decrypt the same file with the same parameters, I get my input back. Where the in.txt file contains my input, I get an output file with gibberish. Now the secret file can be decrypted, using the symmetric key: $ openssl aes-256-cbc -d -in -out secretfile.txt -pass file:secret.keyĪgain, here the encrypted file is and the unencrypted file will be named secretfile.I am testing OpenSSL by executing the Known Answer tests provided here. But this is the path to where it usually is located. The recipient should replace ~/.ssh/id_rsa with the path to their secret key if needed. Decrypt a file encrypted with a public SSH keyįirst decrypt the symmetric.key: $ openssl rsautl -decrypt -oaep -inkey ~/.ssh/id_rsa -in -out secret.key
OPENSSL ENCRYPT FILE DOWNLOAD
It is even safe to upload the files to a public file sharing service and tell the recipient to download them from there. Now you can send the encrypted secret file () and the encrypted symmetric key () to the recipient. Replace recipients-key.pub with the recipient’s public SSH key.ĭelete the unencrypted symmetric key, so you don’t leave it around: $ rm secret.key The encrypted file can be named whatever you like.Įncrypt the symmetric key, using the recipient’s public SSH key: $ openssl rsautl -encrypt -oaep -pubin -inkey <(ssh-keygen -e -f recipients-key.pub -m PKCS8) -in secret.key -out In this example secretfile.txt is the unencrypted secret file, and is the encrypted file. If you send something to the recipient at another time, don’t reuse it.Įncrypt the file you’re sending, using the generated symmetric key: $ openssl aes-256-cbc -in secretfile.txt -out -pass file:secret.key You should only use this key this one time, by the way. Generate the symmetric key (32 bytes gives us the 256 bit key): $ openssl rand -out secret.key 32 This is how encrypted connections usually work, by the way. For this reason, we’ll actually generate a 256 bit key to use for symmetric AES encryption and then encrypt/decrypt that symmetric AES key with the asymmetric RSA keys. size of a file – that can be encrypted using asymmetric RSA public key encryption keys (which is what SSH keys are). There is a limit to the maximum length of a message – i.e. But if you already have someone’s public SSH key, it can be convenient to use it, and it is safe. If you encrypt/decrypt files or messages on more than a one-off occasion, you should really use GnuPGP as that is a much better suited tool for this kind of operations. They can then use their private key to decrypt the file you sent. If you have someone’s public SSH key, you can use OpenSSL to safely encrypt a file and send it to them over an insecure connection (i.e.