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90 lines
2.9 KiB
Plaintext
90 lines
2.9 KiB
Plaintext
USB communication (current)
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===========================
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* Get response, command chaining, short APDU only.
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If it were only for token and no smartcard:
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* Get response, command chaining and short APDU would be considered
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useless.
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* It would be wise to use extended APDU and CCID/ICCD block chaining.
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The question would be: When lower layer (CCID/ICCD layer) support
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enough mechanism of block assembly, why not use one in the application
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layer (ISO 7816)?
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For token implementation, CCID/ICCD would be lower layer and ISO 7816
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would be higher layer, but it's different in fact. The figure of
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communication is like::
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host <-----------> reader <---------> smartcard
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CCID/ICCD ISO 7816
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host <--> token
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Given the situation host side (GnuPG) already has the features of
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handling get response, command chaining, and short APDU only, it is
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rather better to do that on token side too.
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Besides, supporting extended APDU on host side, it would be needed to
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prepare 64KB buffer (that's the maximum size), as there is no explicit
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limitation for buffer size. 64KB would be large, and this could be
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avoided when we use short APDU only.
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USB communication (second attempt)
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==================================
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* No get response, no command chaining, but extended APDU and extended
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Lc and Le. I think that this keep the code simple.
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* The value of dwMaxCCIDMessageLength is 320, that's the size
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of header of ICC block plus size of maximum APDU (by 64
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granularity). Still, some ccid implementation (ccid 1.3.11, for
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example) sends ICC block using chaining unfortunately, so we keep
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the code of ICC block chaining.
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USB communication (initial attempt)
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===================================
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* Once in the past (version <= 0.4), the value of
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dwMaxCCIDMessageLength was 64 and we supported CCID/ICCD block chaining,
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so that we could not handle multple Bulk transactions.
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OpenPGP card protocol implementation
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====================================
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I try to follow "no clear password(s)" policy, even if it is on
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protected flash memory. Further, keystrings for user and reset code
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are removed after key imports. Because of this, replacing keys are
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not possible without password information. (Thus, replacing existing
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keys are not supported.)
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Therefore, there is "no clear password" and "no keystrings" on flash
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ROM when Gnuk is used by admin-less mode. When it is used with admin,
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the keystring of admin is on flash ROM.
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How a private key is stored
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===========================
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KEYPTR
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----> [ P ][ Q ][ N ]
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<---encrypted----><--- plain ---->
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key_addr 4-byte
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initial_vector (random) 16-byte
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checksum_encrypted 16-byte
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dek_encrypted_by_keystring_pw1 16-byte
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dek_encrypted_by_keystring_rc 16-byte
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dek_encrypted_by_keystring_pw3 16-byte
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... decrypted to
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[ P ][ Q ]
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checksum 16-byte
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