When converting a password-protected PEM/PKCS1-encoded private key to DER format one is not able to encrypt the key, OpenSSL automagically asks for the password and writes the plain-text key in the output file.
However, I understand that PKCS8-encoding does support encryption when converted to DER format, my problem is that I can't make OpenSSL write an encrypted file. I have tried:
openssl pkey -inform PEM -in key_pkcs8_encrypted.pem -outform DER -out key_pkcs8_encrypted.der
...but OpenSSL asks for the password and writes a decrypted file (verified by diffing it with the DER version of the decrypted PEM key).
I have also tried:
openssl rsa -des3 -in key_pkcs8_unencrypted.pem -outform DER -out key_pkcs8_encrypted.der
...in the hope that OpenSSL would ask for a password and encrypt the output file, as it does in the -outform PEM case but it does not, it just writes an unencrypted file.
And finally I have tried:
openssl rsa -des3 -in key_pkcs8_unencrypted.pem -passout pass:mypassword -outform DER -out key_pkcs8_encrypted.der
...but that also writes an unencrypted file.
Am I correct that PEM/PKCS8 when converted to DER does support encryption and, if so, does anyone know how I might persuade OpenSSL to do it for me?
Edit: I am aware of this post but it doesn't address the part about how OpenSSL can be asked to generate a password-protected DER file.
openssl pkcs8 -topk8 -inform pem -in key_pkcs1_encrypted.pem -outform DER -out key_pkcs8_encrypted.derand that asked for both decryption and encryption passwords, plus the DER file is now different, so I guess that's done it?pkey [-outform pem]writes PKCS8 PEM and can be encrypted, butpkey -outform derwrites traditional DER for most algorithms (PKCS1 for RSA, SEC1 for ECC, adhoc for DSA) which cannot, but since OpenSSL had no traditional key format for DH it writes that as PKCS8 (but still doesn't encrypt!).pkcs8 -topk8 -outform deris indeed the only way at commandline to create PKCS8-encrypted DER. (rsaand alsogenrsawrites traditional PEM or traditional=PKCS1 DER, never any PKCS8.) ...pkey -inform deruses an awful kludge calledd2i_AutoPrivateKeyand can actually read all traditional formats and PKCS8-clear but not PKCS8-encrypted, as you tried. Bleah. Do you have any doc, or examples, of what these devices want?