If you are using last Magento version, or have just updated your old installation, you could come on this error when try to load an extension through magento connect, with the error “Unknown cipher in list: TLSv1”, and this will happen with near all extensions.

The fix for this is quite simple, but require to edit a magento core file, so please backup it befor and take care of what you’ll do.

In downloader/lib/Mage/HTTP/Client/Curl.php, try changing:

$this->curlOption(CURLOPT_SSL_CIPHER_LIST, 'TLSv1');

to

$this->curlOption(CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);

Save, uploade the changed file and try again, now all should have been fixed and you’ll be able again to install your Magento extensions using Magento connect.