Andrew Boyson / crypto

A simple library to support serving https.

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explanation.txt@19:f22327e8be7b, 2019-10-15 (annotated)

Committer:
andrewboyson
Date:
Tue Oct 15 07:26:15 2019 +0000
Revision:
19:f22327e8be7b
Parent:
14:03a0b8fd6ddc 
Pulled AES128_CBC_SHA1 into its own routines to keep it apart from future work.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 19:f22327e8be7b 1 Ciper and MAC keys lengths
andrewboyson 19:f22327e8be7b 2 ==========================
andrewboyson 19:f22327e8be7b 3
andrewboyson 19:f22327e8be7b 4 Key IV Block
andrewboyson 19:f22327e8be7b 5 Cipher Type Material Size Size
andrewboyson 19:f22327e8be7b 6 ------------ ------ -------- ---- -----
andrewboyson 19:f22327e8be7b 7 NULL Stream 0 0 N/A
andrewboyson 19:f22327e8be7b 8 RC4_128 Stream 16 0 N/A
andrewboyson 19:f22327e8be7b 9 3DES_EDE_CBC Block 24 8 8
andrewboyson 19:f22327e8be7b 10 AES_128_CBC Block 16 16 16
andrewboyson 19:f22327e8be7b 11 AES_256_CBC Block 32 16 16
andrewboyson 19:f22327e8be7b 12
andrewboyson 19:f22327e8be7b 13
andrewboyson 19:f22327e8be7b 14 MAC Algorithm mac_length mac_key_length
andrewboyson 19:f22327e8be7b 15 -------- ----------- ---------- --------------
andrewboyson 19:f22327e8be7b 16 NULL N/A 0 0
andrewboyson 19:f22327e8be7b 17 MD5 HMAC-MD5 16 16
andrewboyson 19:f22327e8be7b 18 SHA HMAC-SHA1 20 20
andrewboyson 19:f22327e8be7b 19 SHA256 HMAC-SHA256 32 32
andrewboyson 19:f22327e8be7b 20
andrewboyson 19:f22327e8be7b 21
andrewboyson 6:819c17738dc2 22 Names
andrewboyson 6:819c17738dc2 23 =====
andrewboyson 0:be515c9019e3 24 SHA
andrewboyson 0:be515c9019e3 25 secure hash algorithm
andrewboyson 0:be515c9019e3 26 - it is deterministic, meaning that the same message always results in the same hash
andrewboyson 0:be515c9019e3 27 - it is quick to compute the hash value for any given message
andrewboyson 0:be515c9019e3 28 - it is infeasible to generate a message that yields a given hash value
andrewboyson 0:be515c9019e3 29 - it is infeasible to find two different messages with the same hash value
andrewboyson 0:be515c9019e3 30 - a small change to a message should change the hash value so extensively that
andrewboyson 0:be515c9019e3 31 the new hash value appears uncorrelated with the old hash value (avalanche effect)
andrewboyson 0:be515c9019e3 32
andrewboyson 0:be515c9019e3 33 HMAC
andrewboyson 0:be515c9019e3 34 keyed-hash message authentication code or hash-based message authentication code
andrewboyson 0:be515c9019e3 35 - it is a message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key.
andrewboyson 0:be515c9019e3 36 - it may be used to simultaneously verify both the data integrity and the authentication of a message
andrewboyson 2:82268409e83f 37 - used to sign a message with a symmetrical key
andrewboyson 6:819c17738dc2 38
andrewboyson 6:819c17738dc2 39
andrewboyson 6:819c17738dc2 40 Links
andrewboyson 6:819c17738dc2 41 =====
andrewboyson 6:819c17738dc2 42 https://tls.ulfheim.net/
andrewboyson 6:819c17738dc2 43
andrewboyson 2:82268409e83f 44 Full RSA handshake
andrewboyson 2:82268409e83f 45 ===================
andrewboyson 8:5e66a6b4b38c 46 ClientHello -=> use session id to jump to short handshake
andrewboyson 8:5e66a6b4b38c 47 <=- ServerHello
andrewboyson 8:5e66a6b4b38c 48 <=- Certificate
andrewboyson 8:5e66a6b4b38c 49 <=- ServerHelloDone
andrewboyson 6:819c17738dc2 50
andrewboyson 8:5e66a6b4b38c 51 ClientKeyExchange -=> start asynchronous sha256 decryption
andrewboyson 6:819c17738dc2 52 ChangeCipherSpec --> switch to encrypedIn
andrewboyson 8:5e66a6b4b38c 53 Finished -=> store the encrypted verify message
andrewboyson 6:819c17738dc2 54
andrewboyson 6:819c17738dc2 55 sha256 decrypted --> prepare the keys and decrypt the verify message
andrewboyson 2:82268409e83f 56 <-- ChangeCipherSpec
andrewboyson 8:5e66a6b4b38c 57 <=- Finished
andrewboyson 2:82268409e83f 58
andrewboyson 2:82268409e83f 59
andrewboyson 2:82268409e83f 60 Short RSA handshake
andrewboyson 2:82268409e83f 61 ===================
andrewboyson 8:5e66a6b4b38c 62 ClientHello -=>
andrewboyson 8:5e66a6b4b38c 63 <=- ServerHello
andrewboyson 2:82268409e83f 64 <-- ChangeCipherSpec
andrewboyson 8:5e66a6b4b38c 65 <=- Finished
andrewboyson 14:03a0b8fd6ddc 66 ChangeCipherSpec --> switch to encrypedIn
andrewboyson 8:5e66a6b4b38c 67 Finished -=>
andrewboyson 2:82268409e83f 68