Ludovic Rousseau's blog: ATR parsing in JSON

Friday, May 20, 2022

ATR parsing in JSON

I updated my ATR parsing web site at https://smartcard-atr.apdu.fr/ to add the option to get the result not in an HTML page but as a JSON document.

If you do not yet know this service you can read "Parsing an ATR: new web site URL" to get some history.

JSON

The URL for the JSON service is https://smartcard-atr.apdu.fr/V1/parse2json?ATR=3BFF9700008131FE4380318065B0846160FB120FFD8290000D.

It is the same as for the HTML output https://smartcard-atr.apdu.fr/parse?ATR=3BFF9700008131FE4380318065B0846160FB120FFD8290000D except you replace "parse" by "V1/parse2json" in the URL.

Of course you update the ATR parameter value to use the ATR value you want to parse.

Examples

You can use it to get the description of a particular field by piping the result in the jq command.

jq is a lightweight and flexible command-line JSON processor.

For example to get the meaning of the TA₁ byte you can use:

$ curl -s https://smartcard-atr.apdu.fr/V1/parse2json?ATR=3B12953606 | jq '.TA."1"'
{
  "description": "Fi=512, Di=16, 32 cycles/ETU (125000 bits/s at 4.00 MHz, 156250 bits/s for fMax=5 MHz)",
  "value": 149
}

Or for just the TA₁ description:

$ curl -s https://smartcard-atr.apdu.fr/V1/parse2json?ATR=3B90160187 | jq '.TA."1".description'
"Fi=372, Di=32, 11.625 cycles/ETU (344086 bits/s at 4.00 MHz, 430107 bits/s for fMax=5 MHz)"

Card matching

I also added the possibility to get the cards matching a given ATR.

For example: https://smartcard-atr.apdu.fr/V1/match?ATR=3B8F800180318065B0850300EF120FFE82900072

$ curl -s https://smartcard-atr.apdu.fr/V1/match?ATR=3B8F800180318065B0850300EF120FFE82900072 | jq
{
  "3B 8F 80 01 80 31 80 65 B0 .. .. .. .. 12 0F FE 82 90 00 ..": [
    "IDPrime MD 3810 T=Contactless (Prox DU)"
  ],
  "3B 8F 80 01 80 31 80 65 B0 85 03 00 EF 12 0F FE 82 90 00 72": [
    "Gemalto IDPrime MD 3840",
    "http://www.gemalto.com/dwnld/6891_IDPrimeMD3840_Product_Datasheet_May14.pdf"
  ]
}

Because of the joker mechanism using the character '.' it is possible that one ATR matches more than one "card".