namespace check: encryption.xml EncryptionProperty > ns:Compression (ns = http://www.idpf.org/2016/encryption#compression)

[danielweck]

Let's open this issue to track whether or not the LCP server implementation is using the correct namespace for encryption.xml's custom element EncryptionProperty > ns:Compression, which currently is http://idpf.org/ocf/encryption#compression (reminder: this is where the attributes Method and OriginalLength are used to cover the optional deflate+compress+store case)

The IDPF specification currently does not normatively define this namespace, so we need a fallback strategy. I suggest a readium.org namespace, similar to that used for LCP. This would impact the source code:
https://github.com/readium/readium-lcp-server/blob/feature/compress-before-encryption/xmlenc/encryption.go#L120

type EncryptionProperty struct {
    Compression Compression `xml:"http://idpf.org/ocf/encryption#compression Compression"`
}

...and of course Readium's own implementation:
https://github.com/readium/readium-sdk/blob/develop/ePub3/ePub/encryption.cpp#L27

#define ReadiumURI "http://readium.org/2015/01/lcp#extendedProperty"

(as you can see, there's already an inconsistency!)

Full EPUB issue:
w3c/epub-specs#646 (comment)

[danielweck]

I opened an issue in the ReadiumSDK repository:
readium/readium-sdk#230

[danielweck]

Regarding the Compression XML element namespace, @mattgarrish says that it's either http://www.idpf.org/2016/encryption#compression (to follow existing conventions) or http://www.idpf.org/ns/encryption#compression (new non-dated URI convention)
See w3c/epub-specs#646 (comment)

[danielweck]

EPUB 3.1 draft update:
http://rawgit.com/IDPF/epub-revision/master/build/31/spec/epub-ocf.html#sec-enc-compression
(Compression element namespace is http://www.idpf.org/2016/encryption#compression )

[danielweck]

Related issue (thanks @drmnside @thkim2015) w3c/epub-specs#697

[danielweck]

Updated source code reference:
https://github.com/readium/readium-lcp-server/blob/master/xmlenc/encryption.go#L130

type Compression struct {
    Method         int    `xml:"Method,attr"`
    OriginalLength uint64 `xml:"OriginalLength,attr"`
}

type EncryptionProperty struct {
    Compression Compression `xml:"http://idpf.org/ns/encryption#compression Compression"`
}

type EncryptionProperties struct {
    Properties []EncryptionProperty `xml:"http://www.w3.org/2001/04/xmlenc# EncryptionProperty"`
}

type Data struct {
    encryptedType
    Properties *EncryptionProperties `xml:"http://www.w3.org/2001/04/xmlenc# EncryptionProperties,omitempty"`
}

[danielweck]

The IDPF-endorsed XML namespace is http://www.idpf.org/2016/encryption#compression
See: http://rawgit.com/IDPF/epub-revision/master/build/31/spec/epub-ocf.html#sec-enc-compression

@jpbougie could you please update:
https://github.com/readium/readium-lcp-server/blob/master/xmlenc/encryption.go#L130

type EncryptionProperty struct {
    Compression Compression `xml:"http://idpf.org/ns/encryption#compression Compression"`
}

Many thanks!

[jpbougie]

Fixed with 91cd5b1