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The .tel platform includes a friending mechanism for controlling access to published contact information. In fact, any NAPTR data can be secured and made private to any friend. For example, if Alice owns and she has friends Bob and Charlie, she could make her office telephone number public, restrict her email address to be shown only to Bob and Charlie, and make her home phone number viewable only by Bob.

Private data is encrypted and stored inside NAPTR records of type "x-crypto". The X-Crypto NAPTR has been designed not to break IANA ENUM service type formats and abide by the IETF "ENUM Experiences" document.

The process to secure data consists of three procedures that are performed by the encryption routines:

  1. The plaintext is processed with PKCS#1.5 or OAEP padding to provide extra protection against attack and create a standard block size (in this case 128 bytes).
  2. The plaintext is 1024-bit encrypted with the reader's public key to obtain 128 bytes of binary data.
  3. The binary data is Base 64 encoded so that the encrypted data can be stored in a NAPTR record without containing special characters.

Note: We do NOT recommend storing sensitive personal information such as credit card numbers inside a .tel domain. This is not the purpose of the .tel.

The public-private key pair technique can be used for secure data exchange bypassing the “official” .tel friending system. All you need to know is how to decrypt your friend’s encrypted data.

Related Links
ENUM Experiences: IETF Document on ENUM issues and experiences
Whitepaper: Protecting .tel Contact Data
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