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Update to support the viewkey encodings in zcash/zips/#117 #8

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FiloSottile merged 3 commits into from
Feb 23, 2017
Merged

Update to support the viewkey encodings in zcash/zips/#117 #8

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fe14ea3
Update to support the viewkey encodings in zcash/zips/#117
zmanian Feb 21, 2017
2d75bc1
Clamp the output of addrPRF(1) in the view key to a valid Curve25519
zmanian Feb 23, 2017
1cc534d
Minor comment change
FiloSottile Feb 23, 2017
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13 changes: 10 additions & 3 deletions zcash/address.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,8 @@ var (
TestSpendingKey = [2]byte{0xAC, 0x08}
ProdAddress = [2]byte{0x16, 0x9A}
TestAddress = [2]byte{0x16, 0xB6}
ProdViewingKey = [2]byte{0, 0} // Not yet specified - WILL CHANGE
ProdViewingKey = [2]byte{0x0B, 0x1C}
TestViewingKey = [2]byte{0x0B, 0x2A}
)

var (
Expand Down Expand Up @@ -96,8 +97,14 @@ func KeyToViewingKey(key []byte) ([]byte, error) {
if len(key) != 32 || key[0]&0xf0 != 0 {
return nil, ErrInvalidKey
}
viewKey := make([]byte, 32)
prfAddr(viewKey, key, 1)
viewKey := make([]byte, 64)
prfAddr(viewKey, key, 0)
prfAddr(viewKey[32:], key, 1)
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@str4d str4d Feb 23, 2017

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Per sections 4.2 and 5.4.6 of the Zcash spec, the output of prfAddr(_, key, 1) needs to be clamped to a valid Curve25519 secret key in order to match the definition of sk_enc. I'm guessing this was unnecessary in askToPKenc() because curve25519.ScalarBaseMult() performs clamping internally.

// Clamp PRF output to a valid Curve25519 secret key.
// (See sections 4.2 and 5.4.6 of the Zcash spec.)
viewKey[32] &= 248
viewKey[63] &= 127
viewKey[63] |= 64
return viewKey, nil
}

Expand Down