Zend_Crypt_Rsa - Pádraic Brady

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Zend_Crypt_Rsa
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[Pádraic Brady|mailto:padraic.brady@yahoo.com]
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1.0 - 12 June 2008: Ready for review
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Zend_Crypt_Rsa is an implementation of the RSA algorithm for public-key cryptography. This proposal assumes a dependency on PHP's OpenSSL extension, though a later adapter would allow operation even in the absence of OpenSSL, or outside the limitations that OpenSSL imposes. The purpose of the proposal is to write an OO wrapper around the existing ext/openssl functionality where keys are represented as discrete objects rather than resources and strings. Both public and private keys utilise a common interface supporting common encryption, decryption, data signing and key generation and can be directly echoed as PEM strings for remote storage. The main input source at present is also PEM - certificate import is a simple addition once the base functionality is complete.
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{zone-data:requirements}
* This component *will* utilise ext/openssl is available
* This component *will* support dual path encryption/decryption
* This component *will* support generating signed data signatures
* This component *will* generate key pairs for any bit-length > 384 bits
* This component *will not currently* generate keys with less than 384 bits
* This component *will not currently* operate in the absence of ext/openssl
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* Zend_Exception
* ext/openssl
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The component operates in a simple manner. The Zend_Crypt_Rsa object is instantiated usually by passing the PEM representation string of a private key, from which both the private key itself, and the respective public key, are in turn instantiated as separate objects of type Zend_Crypt_Key. Key objects share a common interface, and can be echoed directly back into the PEM format.

Once instantiated the object is capable of performing a wide range of common RSA operations including signing data, key generation, encryption and decryption. Both encryption and decryption operations require users to explicitly pass the key to use for both processes, to facilitate either public key, or private key, based encryption.
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{zone-data:milestones}
* Milestone 1: [DONE] Assemble use cases and design comments based on draft source code
* Milestone 2: [DONE] Assemble a unit test suite
* Milestone 3: [UNDERWAY/PENDING COMMENT] Complete initial development
* Milestone 4: Verify unit test coverage
* Milestone 5: Write documentation
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* Zend_Crypt_Rsa
* Zend_Crypt_Rsa_Exception
* Zend_Crypt_Rsa_Key
* Zend_Crypt_Rsa_Key_Private
* Zend_Crypt_Rsa_Key_Public

This is a preliminary class listing. Pending public and Zend review, the list may expand as necessary.
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||UC-01||

Simple key generation.

{code}
<?php

$rsa = new Zend_Crypt_Rsa;
$keys = $rsa->generateKeys(array('private_key_bits'=>512));
echo $keys->privateKey; // PEM string
echo $keys->publicKey; // PEM string
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||UC-02||

Data signing for secure message exchanges.

{code}
<?php

$dataToSend = '1234567890';
$rsa = new Zend_Crypt_Rsa('/path/to/privatekey.pem');
$binarySignature = $rsa->sign($dataToSign);
$base64Signature = $rsa->sign($dataToSign, Zend_Crypt_Rsa::BASE64);
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||UC-03||

Verifying received data using the signature also sent with message.

{code}
<?php

$dataReceived = '1234567890';
$signatureReceived = 'XXXXXXXXXXXXXXXXXXXXXXX'; //assume some binary signature
$rsa = new Zend_Crypt_Rsa('/path/to/privatekey.pem');
$result = $rsa->verifySignature($dataReceived, $signatureReceived);
var_dump($result); // TRUE or FALSE
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||UC-04||

Public key encryption for public messaging of secure data.

{code}
<?php

$rsa = new Zend_Crypt_Rsa('/path/to/privatekey.pem');
$dataToEncrypt = '1234567890';
$encrypted = $rsa->encrypt($data, $rsa->getPublicKey());
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||UC-05||

Decrypting UC-04 result.

{code}
<?php

$encrypted = 'XXXXXXXXXXXXXXXXXXXXXX'; // assume encrypted data
$rsa = new Zend_Crypt_Rsa('/path/to/privatekey.pem');
$decrypted = $rsa->decrypt($data, $rsa->getPrivateKey());
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||UC-06||

All keys can be queried for their PEM string forms, their respective OpenSSL Key resources, and bit length.

{code}
<?php

$rsa = new Zend_Crypt_Rsa('/path/to/privatekey.pem');
echo $rsa->getPublicKey(); // PEM string
echo count($rsa->getPrivateKey()); // bit count, class implemented Countable
echo get_resource_type($rsa->getPublicKey()->getOpensslKeyResource()); // Openssl key resource
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