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Thread: Generate digital signature from a string

  1. #1
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    Default Generate digital signature from a string

    Hi all,

    I have a private key file (.pem) and a self-signed certificate file (.pem). I need to sign a string using both files, how can I do this? till now I can generate a digital signature using the private key but it's not working. How to use the certificate file in this case? knowing that the format of the signed data should be PKCS#7

    Thanks in advance,
    Joud

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    Default Re: Generate digital signature from a string

    Can you post the code you are having problems with and describe what the problem is?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Generate digital signature from a string

    It's really long and complicated. Let me rephrase the question:
    - I, the client, have generated a self-signed certificate with private key using openssl.
    - The certificate has been imported to the server to which I need to do http Get and Post requests (which will be signed - with a signature parameter passed) - and the certificate will be used to verify the signature.
    - I generated the signature from a message using the private key.

    My question is, do I need to use the certificate from my side for generating the digital signature? or the private key is enough? How the server will recognize what certificate to use for verification? This is the first time I work with certificates.

    Here's the simple code I use:

    String message = 'some message'
    //Load the private key from pem file
    PrivateKey privateKey = loadPrivateKey()
    //Sign the message
    Signature signature = Signature.getInstance("SHA256withRSA")
    signature.initSign(privateKey);
    signature.update(message.getBytes());
    byte[] signedMsg = signature.sign();

    Thanks in advance
    Last edited by Joud; September 12th, 2018 at 10:59 AM.

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    Super Moderator Norm's Avatar
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    Default Re: Generate digital signature from a string

    Sorry, I don't know anything about servers and certificates.
    If you don't understand my answer, don't ignore it, ask a question.

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