>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #2943231. --> Reported by: [gambry](https://www.drupal.org/user/400462) >>> <h3 id="summary-problem-motivation">Problem/Motivation</h3> <p>The current interfaces on Encryption module - and all the implementations I've seen so far - don't take in consideration public key cryptography.</p> <p>"Public key cryptography, or asymmetrical cryptography, is any cryptographic system that uses pairs of keys: public keys which may be disseminated widely, and private keys which are known only to the owner." <a href="https://en.wikipedia.org/wiki/Public-key_cryptography">source Wikipedia.</a></p> <p>Currently the module description page clearly states "Encrypt is a Drupal module that provides an application programming interface (API) for performing two-way data encryption", which presume we exclude asymmetrical cryptography, when the user want to use only the public key and so only encrypt the data.</p> <p>To be honest currently implementing two-way encryption is not 100% safe, as the key to encrypt as well as decrypt is stored in the same instance. This can be mitigated by not storing the key anywhere in the current machine and making sure it's not cached anyway, as well as storing the key on 3rd party services.</p> <p>I'm the maintainer of the <a href="https://www.drupal.org/project/encrypt_rsa">Encrypt RSA</a>, which allow users to use a Private key to encrypt/decrypt as well as just the public key to encrypt-only their data.</p> <h3 id="summary-proposed-resolution">Proposed resolution</h3> <p>My suggestion is to:</p> <ul> <li>introduce a flag/method in the <code>EncryptionMethodInterface</code> i.e. <code>::canDecrypt()</code> to check if method can actually decrypt</li> <li>Raise an exception when "encryption" service try to decrypt through a method with <code>::canDecrypt()</code> FALSE.</li> <li>Extend <code>EncryptionMethodInterface::decrypt()</code> docblock by adding the @throw exception annotation when the method can't decrypt</li> <li>Adding some test coverage</li> <li>Update the module description and documentation, flagging it supports Public-key cryptography as well and so don't assume decryption is always possible</li> <li>Advertisting a bit this change, mainly to increase the knowledge around asymmetrical cryptography</li> </ul> <h3 id="summary-remaining-tasks">Remaining tasks</h3> <ul> <li><del>introduce a flag/method in the <code>EncryptionMethodInterface</code> i.e. <code>::canDecrypt()</code> to check if method can actually decrypt</del></li> <li><del>Raise an exception when "encryption" service try to decrypt through a method with <code>::canDecrypt()</code> FALSE.</del></li> <li><del>Extend <code>EncryptionMethodInterface::decrypt()</code> docblock by adding the @throw exception annotation when the method can't decrypt</del></li> <li><del>Adding some test coverage</del></li> <li><del>Update the module <del>README.md</del>, description and documentation, flagging it supports Public-key cryptography as well and so don't assume decryption is always possible</del></li> <li>Getting in touch with the main contrib modules providing Encryption Methods and for the module to be listed in Encrypt project page it needs to include a small template/widget/bullet-list (TBD) where it says: Encryption Method being used, link to the method documentation, Can decrypt? Yes/No.</li> </ul> <h3 id="summary-ui-changes">User interface changes</h3> <p>No.</p> <h3 id="summary-api-changes">API changes</h3> <p>A new Encryption Method property definition <code>can_decrypt</code> and a new <code>EncryptionMethodInterface::canDecrypt()</code> method have been created. They are TRUE by default.</p> <h3 id="summary-data-model-changes">Data model changes</h3> <p>No.</p> > Related issue: [Issue #2925621](https://www.drupal.org/node/2925621)