3-KeyUsage.md

TLS Certificates 101 Workshop

Part 3: Key Usage

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Encrypt and Decrypt a Message

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Create a message

$ echo "Hello World" > message.txt

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Symetric Encryption & Decryption / ist das wirklioch symmetrisch?

Encrypt the message using the Private Key

$ openssl pkeyutl -encrypt -inkey private.pem -in message.txt -out message.sym-enc

Decrypt the message using the Private Key

$ openssl pkeyutl -decrypt -inkey private.pem -in message.sym-enc

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Asymetric Encryption & Decryption

Encrypt the message using the Public Key.

$ openssl pkeyutl -encrypt -inkey public.pem -pubin -in message.txt -out message.asym-enc

Decrypt the message using the Private Key

$ openssl pkeyutl -decrypt -inkey private.pem -in message.asym-enc

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Sign and Verify a Message

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Signing

Sign the message using the Private Key.

$ openssl dgst -sha256 -sign private.pem -out message.sig message.txt

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Verification

Verify the message signature using the Public Key.

$ openssl dgst -verify public.pem -signature message.sig message.txt
Verified OK

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Tamper with the message

Modify the message.

$ echo "!" >> message.txt

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Detect Tampering

Verify the message again using the Public Key.

$ openssl dgst -verify public.pem -signature message.sig message.txt
Verification Failure

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Finished!

This was the third part of the workshop.

You should now have learned how to use cryptographic keys for encryption, decryption, signing, and verification.

To continue with the workshop, please proceed to the next part: Certificates