“We intent to begin on the first of February unrestricted submarine warfare. We shall endeavor in spite of this to keep United States of America neutral. In the event of this not succeeding, we make Mexico a proposal of alliance on the following basis: make war together, make peace together, generous financial support and an understanding on our part that Mexico is to reconquer the lost territory in Texas, New Mexico, and Arizona. The settlement in detail is left to you. You will inform the President of the above most secretly as soon as the outbreak of war with the United States of America is certain and add the suggestion that he should, on his own initiative, invite Japan to immediate adherence and at the same time mediate between Japan and ourselves. Please call the President’s attention to the fact that the ruthless employment of our submarines now offers the prospect of compelling England in a few months to make peace.” Signed, ZIMMERMANN.
The type of encryption used for this telegram was symmetric. The reason I believe that the message was considered symmetric is because in symmetric encryption a message is sent in cipher text and the person that is meant to receive the message has a code to convert the message from Cipher text to plain text. This is the method that Zimmermann used in his telegram. Zimmerman and the intended receiver of the message shared the key that decrypted the message from cipher text to plain text. Therefore the telegram used symmetric encryption. Asymmetric encryption can be ruled out due to the fact in asymmetric encryption requires two separate keys; one being public and one private. The public key is available for everyone while the private key is only known by the owner. This method of encryption was not used in Zimmermann’s telegram.
As far as which encryption method is better, I would have to say that asymmetric is better than symmetric due to the fact that it requires two keys
References: Czagan, D. (2013, October 23). Symmetric and Asymmetric Encryption - InfoSec Institute. Retrieved October 2, 2014, from http://resources.infosecinstitute.com/symmetric-asymmetric-encryption/ Description of Symmetric and Asymmetric Encryption. (n.d.). Retrieved October 2, 2014, from http://support2.microsoft.com/kb/246071