A large amount of files were encrypted by 

        openssl enc -aes-256-cbc -pass pass:MYPASSWORD

Openssl should derive key+IV from passphrase. **I'd like to know key+IV equivalent of that MYPASSWORD**. Is that possible? 

I know MYPASSWORD. I could decrypt and then re-encrypt with new known key+IV with:

        openssl enc -d -aes-256-cbc -pass pass:MYPASSWORD
        openssl enc -aes-256-cbc -K MYKEY -IV MYIV

But the problem is that the amount of data is quite large.