STS Association Wiki

EA - Encryption Algorithm

Algorithm types

Various algorithms exist in a STS based system:

  1. ​Algorithms used to create decoder keys from vending keys (DKGA = Decoder Key Generation ALgorithm)
  2. Encryption Algorithms used to create and/or decrypt tokens in the meter and vending system (EA = Encryption Algorithm)


​Decoder Key Generation Algorithm (DKGA)

​ A DKGA is an algorithm used by the security module to create a decoder key for a payment meter from various input parameters:

  1. International identification number (IIN)
  2. Decoder reference number (DRN)
  3. Key Type (KT)
  4. Tariff index (TI)
  5. Key revision number (KRN)
  6. Vending key (VK)
  7. Supply group code (SGC)
  8. Base date (DKGA04 only)

DKGA's in use:

Currently, the following DKGA's are specified:

  1. DKGA01 (64 bit DES - not reccomended for use)
  2. DKGA02 (64 bit DES - current use)
  3. DKGA03 (triple DES - not recommended for use)
  4. DKGA04 (HMAC-SHA256 - available for use. Recommended for higher levels of security)


​Encryption Algorithm (EA)​

​The following encryption algorithms are specified by the IEC62055-41 specification:

  1. EA07 - the STA algoithm currently in use. This algorithm uses a 64 bit key.
  2. EA11 - the MISTY1 algorithm. This algorithm uses a 128 bit key and is recommended for higher levels of security.

The EA is used to encrypt and decrypt token data in an STS based system:


The following data are used in the encryption of an STS token.