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#1 2009-01-23 22:49:11
- doob
- Member
- Registered: 2008-07-21
- Posts: 15
Differentiating between LF & HF tags
Apologies if I'm stating the obvious, but I don't see it clearly documented anywhere.
A really quick and easy way of determining if a card is HF or LF is to:
1) Run the tune command a couple of times to get an idea of what your voltage readings are on LF and HF.
2) place the unknown card/tag against the proxmark antennas (LF & HF)
3) Run the tune command a couple of times again to get an idea of what the values are wth the tag in the antenna fields
4) Look for significant voltage drops in either HF or LF, the voltage drop indicates the tag operating frequency.
Generally you will see a voltage drop (sometimes over 10 volts) on the corresponding frequency (e.g. LF 125kHz/134kHz, HF 13.56MHz)
Some examples:
Nominal Tune readings (no tags nearby)
# LF antenna @ 26 mA / 33972 mV [1273 ohms] 125Khz
# LF antenna @ 18 mA / 22290 mV [1187 ohms] 134Khz
# HF antenna @ 60 mA / 14276 mV [235 ohms] 13.56Mhz
A HID LF prox card:
# LF antenna @ 8 mA / 10205 mV [1273 ohms] 125Khz [~ 23.5 Volt drop]
# LF antenna @ 9 mA / 11547 mV [1187 ohms] 134Khz [~ 10.7 Volt drop]
# HF antenna @ 60 mA / 14244 mV [235 ohms] 13.56Mhz
An ISO15693 HF prox card:
# LF antenna @ 26 mA / 33837 mV [1273 ohms] 125Khz
# LF antenna @ 18 mA / 22290 mV [1187 ohms] 134Khz
# HF antenna @ 50 mA / 11794 mV [235 ohms] 13.56Mhz [~ 2.5 Volt drop]
An ISO14443A HF tag:
# LF antenna @ 26 mA / 33972 mV [1273 ohms] 125Khz
# LF antenna @ 18 mA / 22155 mV [1187 ohms] 134Khz
# HF antenna @ 44 mA / 10538 mV [235 ohms] 13.56Mhz [~ 3.7 Volt drop]
I think it would be nice to knock out an 'identifytag' command that performed a series of checks including:
1) Power/tuning analysis
2) Modulation detection
3) Vendor/Model enumeration
Rather than use more DSP code to do modulation detection, it would be easier to use the built-in proxmark demodulation commands and code and see which one if any returned reasonable output.
Would be even better to have an 'identifyreader' command...
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