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Create Your Signing Certificate

Digitally signing documents requires a signing certificate in .p12 format. You can either purchase one or create a free self-signed certificate. Follow the steps below to create a free, self-signed certificate for local development.
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Generate Private Key
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Generate a private key using OpenSSL by running the following command:
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openssl genrsa -out private.key 2048
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This command generates a 2048-bit RSA key.
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Generate Self-Signed Certificate
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Using the private key, generate a self-signed certificate by running the following command:
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openssl req -new -x509 -key private.key -out certificate.crt -days 365
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You will be prompted to enter some information, such as the certificate’s Common Name (CN). Ensure that you provide the correct details. The —days parameter specifies the certificate’s validity period.
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Create p12 Certificate
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Combine the private key and the self-signed certificate to create a .p12 certificate. Use the following command:
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openssl pkcs12 -export -out certificate.p12 -inkey private.key -in certificate.crt -legacy
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p12 Certificate Password
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When you create the .p12 certificate, you will be prompted to enter a password. Enter a strong password and keep it secure. Remember this password, as it will be required when using the certificate.
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Note that for local development, the password can be left empty.
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Add Certificate to the Project
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Use the NEXT_PRIVATE_SIGNING_LOCAL_FILE_PATH environment variable to point at the certificate you created.
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Details about environment variables associated with certificates can be found here.