Hi @barbibulle 

**Command:** 
`mp4dash -v -d -f --encryption-key='@skm:https://api.service.expressplay.com/keystore/keys?customerAuthenticator=xxxxxxxxxxxxxxxx#mode=get&kid=0B68C2F889C6A8B6F9A9E99A7B9C53F7&kek=209e1a91e1e897c657214914ddb2a38d&iv=b982e75b2b6a0f5964380501b758bd00' --encryption-cenc-scheme=cbcs --marlin --marlin-add-pssh --playready --playready-add-pssh --playready-header=LA_URL:https://pr-gen.service.expressplay.com --widevine --widevine-header=provider:intertrust#content_id:2a --use-segment-template-number-padding --use-segment-timeline --hls --fairplay-key-uri=skd://expressplay_token /test/abc_1080p_frag.mp4 /test/abc_720p_frag.mp4 /test/abc_480p_frag.mp4 /test/abc_360p_frag.mp4`

When unwrapping key fetched from ExpressPlay KeyStore, latest version (**_Version 2.0.0 r637_**) of Bento4 is giving issue 

```
Response: {"kid":"0B68C2F889C6A8B6F9A9E99A7B9C53F7","kekId":"#1.1a8f0d766d1f678864a2d8b40d1c85a0","ek":"0A2F01C445CF9BC185E26E3627A41014B4DA3B2283706D76","lastUpdate":"2021-01-14T07:34:30Z"}
Traceback (most recent call last):
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 2142, in <module>
    main()
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 1927, in main
    ResolveEncryptionKeys(options)
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 1443, in ResolveEncryptionKeys
    options.key_infos.append(KeySpecToKeyInfo(options, key_spec))
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 1404, in KeySpecToKeyInfo
    kid_hex, key_hex = GetEncryptionKey(options, key_spec[1:])
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4utils.py", line 749, in GetEncryptionKey
    return skm.ResolveKey(options, spec[4:])
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/skm.py", line 195, in ResolveKey
    received_key = UnwrapKey(response_json['ek'], skm_kek)
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/skm.py", line 96, in UnwrapKey
    B = decipher.decrypt(A[0:7] + bytes([A[7]^((n*j)+i+1)])) + R[i:i+1]
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/aes.py", line 289, in decrypt
    raise ValueError('wrong block length, expected ' + str(self.block_size) + ' got ' + str(len(ciphertext)))
ValueError: wrong block length, expected 16 got 8

Process finished with exit code 1
```
Can you please look into this


Issue while Unwrapping Key fetched from KeyStore
This is a GitHub Issue
repo:Bento4
owner:axiomatic-systems
Title : Issue while Unwrapping Key fetched from KeyStore
Issue date:

--- start body ---
Hi @barbibulle 

**Command:** 
`mp4dash -v -d -f --encryption-key='@skm:https://api.service.expressplay.com/keystore/keys?customerAuthenticator=xxxxxxxxxxxxxxxx#mode=get&kid=0B68C2F889C6A8B6F9A9E99A7B9C53F7&kek=209e1a91e1e897c657214914ddb2a38d&iv=b982e75b2b6a0f5964380501b758bd00' --encryption-cenc-scheme=cbcs --marlin --marlin-add-pssh --playready --playready-add-pssh --playready-header=LA_URL:https://pr-gen.service.expressplay.com --widevine --widevine-header=provider:intertrust#content_id:2a --use-segment-template-number-padding --use-segment-timeline --hls --fairplay-key-uri=skd://expressplay_token /test/abc_1080p_frag.mp4 /test/abc_720p_frag.mp4 /test/abc_480p_frag.mp4 /test/abc_360p_frag.mp4`

When unwrapping key fetched from ExpressPlay KeyStore, latest version (**_Version 2.0.0 r637_**) of Bento4 is giving issue 

```
Response: {"kid":"0B68C2F889C6A8B6F9A9E99A7B9C53F7","kekId":"#1.1a8f0d766d1f678864a2d8b40d1c85a0","ek":"0A2F01C445CF9BC185E26E3627A41014B4DA3B2283706D76","lastUpdate":"2021-01-14T07:34:30Z"}
Traceback (most recent call last):
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 2142, in <module>
    main()
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 1927, in main
    ResolveEncryptionKeys(options)
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 1443, in ResolveEncryptionKeys
    options.key_infos.append(KeySpecToKeyInfo(options, key_spec))
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4-dash.py", line 1404, in KeySpecToKeyInfo
    kid_hex, key_hex = GetEncryptionKey(options, key_spec[1:])
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/mp4utils.py", line 749, in GetEncryptionKey
    return skm.ResolveKey(options, spec[4:])
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/skm.py", line 195, in ResolveKey
    received_key = UnwrapKey(response_json['ek'], skm_kek)
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/skm.py", line 96, in UnwrapKey
    B = decipher.decrypt(A[0:7] + bytes([A[7]^((n*j)+i+1)])) + R[i:i+1]
  File "/home/hari/Downloads/Bento4-1-6-0-637/utils/aes.py", line 289, in decrypt
    raise ValueError('wrong block length, expected ' + str(self.block_size) + ' got ' + str(len(ciphertext)))
ValueError: wrong block length, expected 16 got 8

Process finished with exit code 1
```
Can you please look into this


--- end body ---
