Is wireless adb encrypted? When I connect my phone to a new computer's adbd - whether via USB or wireless - it prompts me to confirm the computer's RSA fingerprint. This seems to imply that there is, in some form, cryptography involved in adb communication.

Exactly what does that crypto look like? Is adb traffic encrypted? If I wirelessly pull data via adb from my phone, will someone be able to sample that traffic? Or is it unencrypted, and merely signed?

I searched around, but didn't find any meaningful results (mostly just people talking about disk encryption).
Interesting question, let's just try it out in a practical test. I connected to my device (running Android 5.1.1 Lollipop) through ADB over Wi-Fi using adb connect 10.0.0.10 and ran some tests. What you are seeing is the output of the packets that I captured using Wireshark.

Starting a shell in ADB by sending adb shell:

2290    127.822126  192.168.0.41    10.0.0.10   TCP 85  14804 → 5555 [PSH, ACK] Seq=60 Ack=106 Win=65536 Len=31

0000   90 ef 68 cc f4 48 54 04 a6 a1 a4 3f 08 00 45 00  ..h..HT....?..E.
0010   00 47 63 e1 40 00 80 06 00 00 c0 a8 00 29 0a 00  .Gc.@........)..
0020   00 0a 39 d4 15 b3 57 0e 4a de 41 6b 58 7c 50 18  ..9...W.J.AkX|P.
0030   01 00 cb 14 00 00 4f 50 45 4e 06 00 00 00 00 00  ......OPEN......
0040   00 00 07 00 00 00 52 02 00 00 b0 af ba b1 73 68  ......R.......sh
0050   65 6c 6c 3a 00                                   ell:.


Response received:

2295    127.928185  10.0.0.10   192.168.0.41    TCP 94  5555 → 14804 [PSH, ACK] Seq=130 Ack=91 Win=64256 Len=40

0000   54 04 a6 a1 a4 3f 90 ef 68 cc f4 48 08 00 45 00  T....?..h..H..E.
0010   00 50 2a 73 40 00 3f 06 46 5a 0a 00 00 0a c0 a8  .P*s@.?.FZ......
0020   00 29 15 b3 39 d4 41 6b 58 94 57 0e 4a fd 50 18  .)..9.AkX.W.J.P.
0030   03 ec 74 0a 00 00 57 52 54 45 01 00 00 00 06 00  ..t...WRTE......
0040   00 00 10 00 00 00 81 04 00 00 a8 ad ab ba 72 6f  ..............ro
0050   6f 74 40 72 6b 33 31 38 38 3a 2f 20 23 20        ot@rk3188:/ # 


Writing some text to a file:

816 61.121728   10.0.0.10   192.168.0.41    TCP 190 5555 → 14804 [PSH, ACK] Seq=122 Ack=102 Win=1004 Len=136

0000   54 04 a6 a1 a4 3f 90 ef 68 cc f4 48 08 00 45 00  T....?..h..H..E.
0010   00 b0 2e 7f 40 00 3f 06 41 ee 0a 00 00 0a c0 a8  ....@.?.A.......
0020   00 29 15 b3 39 d4 41 6b 9e 27 57 0e 70 8a 50 18  .)..9.Ak.'W.p.P.
0030   03 ec 69 a3 00 00 57 52 54 45 01 00 00 00 06 00  ..i...WRTE......
0040   00 00 70 00 00 00 04 14 00 00 a8 ad ab ba 0d 72  ..p............r
0050   6f 6f 74 40 72 6b 33 31 38 38 3a 2f 73 64 63 61  oot@rk3188:/sdca
0060   72 64 20 23 20 65 63 68 6f 20 22 54 65 73 74 31  rd # echo "Test1
0070   32 33 22 20 3e 20 74 65 73 74 2e 74 78 74 20 20  23" &gt; test.txt  
0080   20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20                  
0090   20 20 20 20 20 20 20 20 20 20 20 20 20 20 08 08                ..
00a0   08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08  ................
00b0   08 08 08 08 08 08 08 08 08 08 08 08 08 08        ..............


Sending the command for reading out that same file:

1130    71.683380   10.0.0.10   192.168.0.41    TCP 204 5555 → 14804 [PSH, ACK] Seq=2782 Ack=1546 Win=1004 Len=150

0000   54 04 a6 a1 a4 3f 90 ef 68 cc f4 48 08 00 45 00  T....?..h..H..E.
0010   00 be 2e f2 40 00 3f 06 41 6d 0a 00 00 0a c0 a8  ....@.?.Am......
0020   00 29 15 b3 39 d4 41 6b a8 8b 57 0e 76 2e 50 18  .)..9.Ak..W.v.P.
0030   03 ec 35 14 00 00 57 52 54 45 01 00 00 00 06 00  ..5...WRTE......
0040   00 00 7e 00 00 00 cd 12 00 00 a8 ad ab ba 0d 72  ..~............r
0050   6f 6f 74 40 72 6b 33 31 38 38 3a 2f 73 64 63 61  oot@rk3188:/sdca
0060   72 64 20 23 20 63 61 74 20 74 65 73 74 2e 74 78  rd # cat test.tx
0070   74 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20  t               
0080   20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20                  
0090   20 20 20 20 20 20 20 20 20 20 20 20 20 20 08 08                ..
00a0   08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08  ................
00b0   08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08  ................
00c0   08 08 08 08 08 08 08 08 08 08 08 20              ........... 


Received response containing the file's contents (which was written to the console):

1144    72.085985   10.0.0.10   192.168.0.41    TCP 109 5555 → 14804 [PSH, ACK] Seq=2983 Ack=1619 Win=1004 Len=55

0000   54 04 a6 a1 a4 3f 90 ef 68 cc f4 48 08 00 45 00  T....?..h..H..E.
0010   00 5f 2e f7 40 00 3f 06 41 c7 0a 00 00 0a c0 a8  ._..@.?.A.......
0020   00 29 15 b3 39 d4 41 6b a9 54 57 0e 76 77 50 18  .)..9.Ak.TW.vwP.
0030   03 ec b8 6b 00 00 57 52 54 45 01 00 00 00 06 00  ...k..WRTE......
0040   00 00 1f 00 00 00 3f 09 00 00 a8 ad ab ba 54 65  ......?.......Te
0050   73 74 31 32 33 0d 0a 72 6f 6f 74 40 72 6b 33 31  st123..root@rk31
0060   38 38 3a 2f 73 64 63 61 72 64 20 23 20           88:/sdcard # 


Retrieving the file by sending adb pull /sdcard/test.txt:

3711    236.234344  192.168.0.41    10.0.0.10   TCP 102 14804 → 5555 [PSH, ACK] Seq=2776 Ack=4435 Win=255 Len=48

0000   90 ef 68 cc f4 48 54 04 a6 a1 a4 3f 08 00 45 00  ..h..HT....?..E.
0010   00 58 6b 17 40 00 80 06 00 00 c0 a8 00 29 0a 00  .Xk.@........)..
0020   00 0a 39 d4 15 b3 57 0e 7a fc 41 6b af 00 50 18  ..9...W.z.Ak..P.
0030   00 ff cb 25 00 00 57 52 54 45 0a 00 00 00 02 00  ...%..WRTE......
0040   00 00 18 00 00 00 5d 07 00 00 a8 ad ab ba 52 45  ......].......RE
0050   43 56 10 00 00 00 2f 73 64 63 61 72 64 2f 74 65  CV..../sdcard/te
0060   73 74 2e 74 78 74                                st.txt


Received response containing the file's contents:

3717    236.242351  10.0.0.10   192.168.0.41    TCP 94  5555 → 14804 [PSH, ACK] Seq=4491 Ack=2848 Win=1004 Len=40

0000   54 04 a6 a1 a4 3f 90 ef 68 cc f4 48 08 00 45 00  T....?..h..H..E.
0010   00 50 2f e9 40 00 3f 06 40 e4 0a 00 00 0a c0 a8  .P/.@.?.@.......
0020   00 29 15 b3 39 d4 41 6b af 38 57 0e 7b 44 50 18  .)..9.Ak.8W.{DP.
0030   03 ec 8d b1 00 00 57 52 54 45 02 00 00 00 0a 00  ......WRTE......
0040   00 00 10 00 00 00 66 03 00 00 a8 ad ab ba 54 65  ......f.......Te
0050   73 74 31 32 33 0a 44 4f 4e 45 00 00 00 00        st123.DONE....


Conclusion: ADB over Wi-Fi is not encrypted (at least not by default).