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29-648: While XML-DSig is a general framework for digitally signing documents, XAdES specifies precise profiles of XML-DSig making it compliant with the European eIDAS regulation ( Regulation on electronic identification and trust services for electronic transactions in the internal market ). The eIDAS regulation enhances and repeals the Electronic Signatures Directive 1999/93/EC. EIDAS is legally binding in all EU member states since July 2014. An electronic signature that has been created in compliance with eIDAS has

58-449: A decoder that allows invalid byte sequences, one should canonicalize the strings before passing them to the filter. In this context, canonicalization is the process of translating every string character to its single valid byte sequence. An alternative to canonicalization is to reject any strings containing invalid byte sequences. A canonical URL is a URL for defining the single source of truth for duplicate content . A canonical URL

87-433: A given XML Document (an " Infoset ", in common usage among XML developers) may have more than one legal serialized representation. For example, whitespace inside an XML Element is not syntactically significant, so that <Elem > is syntactically identical to <Elem> . Since the digital signature ensures data integrity, a single-byte difference would cause the signature to vary. Moreover, if an XML document

116-523: A non-machine-readable form, too. For example in a guideline . Canonical URLs are usually the URLs that get used for the share action . Since the Canonical URL gets used in the search result of search engines, they are in most cases a landing page . In web search and search engine optimization (SEO), URL canonicalization deals with web content that has more than one possible URL. Having multiple URLs for

145-587: A remote document, which may be rendered in time-varying ways by an errant remote server. To avoid these problems and guarantee that logically-identical XML documents give identical digital signatures, an XML canonicalization transform (frequently abbreviated C14n ) is employed when signing XML documents (for signing the SignedInfo , a canonicalization is mandatory). These algorithms guarantee that semantically-identical documents produce exactly identical serialized representations. Another complication arises because of

174-751: A string containing such glyphs must be considered. To deal with this, Unicode provides the mechanism of canonical equivalence . In this context, canonicalization is Unicode normalization . Variable-width encodings in the Unicode standard, in particular UTF-8 , may cause an additional need for canonicalization in some situations. Namely, by the standard, in UTF-8 there is only one valid byte sequence for any Unicode character, but some byte sequences are invalid, i.e., they cannot be obtained by encoding any string of Unicode characters into UTF-8. Some sloppy decoder implementations may accept invalid byte sequences as input and produce

203-479: A valid Unicode character as output for such a sequence. If one uses such a decoder, some Unicode characters effectively have more than one corresponding byte sequence: the valid one and some invalid ones. This could lead to security issues similar to the one described in the previous section. Therefore, if one wants to apply some filter (e.g., a regular expression written in UTF-8) to UTF-8 strings that will later be passed to

232-572: Is a process for converting data that has more than one possible representation into a "standard", "normal", or canonical form . This can be done to compare different representations for equivalence, to count the number of distinct data structures, to improve the efficiency of various algorithms by eliminating repeated calculations, or to make it possible to impose a meaningful sorting order. Files in file systems may in most cases be accessed through multiple filenames . For instance in Unix -like systems,

261-469: Is clear the file should not be executed. In Unicode , many accented letters can be represented in more than one way. For example, é can be represented in Unicode as the Unicode character U+0065 (LATIN SMALL LETTER E) followed by the character U+0301 (COMBINING ACUTE ACCENT), but it can also be represented as the precomposed character U+00E9 (LATIN SMALL LETTER E WITH ACUTE). This makes string comparison more complicated, since every possible representation of

290-437: Is compulsory only for "qualified" signatures. A "qualified electronic signature" needs to be doted with a digital certificate, encrypted by a security signature creation device, and the identity of the owner of this signing-certificate must have been verified according to the "high" assurance level of the eIDAS regulation. XAdES defines four profiles (forms) differing in protection level offered. In February 2016, ETSI publishes

319-411: Is followed. This procedure establishes whether the resources were really signed by the alleged party. However, because of the extensibility of the canonicalization and transform methods, the verifying party must also make sure that what was actually signed or digested is really what was present in the original data, in other words, that the algorithms used there can be trusted not to change the meaning of

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348-400: Is important for computer security. For example, a web server may have a restriction that only files under the cgi directory C:\inetpub\wwwroot\cgi-bin may be executed. This rule is enforced by checking that the path starts with C:\inetpub\wwwroot\cgi-bin\ and only then executing it. While the file C:\inetpub\wwwroot\cgi-bin\..\..\..\Windows\System32\cmd.exe initially appears to be in

377-420: Is more extensible and geared towards signing XML documents. It is used by various Web technologies such as SOAP , SAML , and others. XML signatures can be used to sign data–a resource –of any type , typically XML documents, but anything that is accessible via a URL can be signed. An XML signature used to sign a resource outside its containing XML document is called a detached signature ; if it

406-673: Is that performing XML canonicalization causes excessive latency that is simply too much to overcome for transactional, performance sensitive SOA applications. These issues are being addressed in the XML Security Working Group . Without proper policy and implementation the use of XML Dsig in SOAP and WS-Security can lead to vulnerabilities, such as XML signature wrapping. An example of applications of XML Signatures: Canonicalization In computer science , canonicalization (sometimes standardization or normalization )

435-450: Is the URL of the page that Google thinks is most representative from a set of duplicate pages on your site. For example, if you have URLs for the same page, such as https://example.com/?dress=1234 and https://example.com/dresses/1234 , Google chooses one as canonical. Note that the pages do not need to be absolutely identical; minor changes in sorting or filtering of list pages do not make

464-492: Is transferred from computer to computer, the line terminator may be changed from CR to LF to CR LF, etc. A program that digests and validates an XML document may later render the XML document in a different way, e.g. adding excess space between attribute definitions with an element definition, or using relative (vs. absolute) URLs, or by reordering namespace definitions. Canonical XML is especially important when an XML Signature refers to

493-398: Is used to sign some part of its containing document, it is called an enveloped signature; if it contains the signed data within itself it is called an enveloping signature. An XML Signature consists of a Signature element in the http://www.w3.org/2000/09/xmldsig# namespace. The basic structure is as follows: When validating an XML Signature, a procedure called Core Validation

522-408: The cgi directory, it exploits the .. path specifier to traverse back up the directory hierarchy in an attempt to execute a file outside of cgi-bin . Permitting cmd.exe to execute would be an error caused by a failure to canonicalize the filename to the simplest representation, C:\Windows\System32\cmd.exe , and is called a directory traversal vulnerability. With the path canonicalized, it

551-447: The document ETSI EN 319 132-1 V1.1.0 as final draft for a European Standard . In this draft, the profiles have been omitted. XML Signature XML Signature (also called XMLDSig , XML-DSig , XML-Sig ) defines an XML syntax for digital signatures and is defined in the W3C recommendation XML Signature Syntax and Processing . Functionally, it has much in common with PKCS #7 but

580-400: The following two snippets of XML: The first example contains extra spaces in the closing tag of the first node. The second example, which has been canonicalized, has had these spaces removed. Note that only the spaces within the tags are removed under W3C canonicalization, not those between tags. A full summary of canonicalization changes is listed below: In morphology and lexicography ,

609-577: The homepage of Misplaced Pages, but a search engine will only consider one of them to be the canonical form of the URL. A Canonical XML document is by definition an XML document that is in XML Canonical form, defined by The Canonical XML specification . Briefly, canonicalization removes whitespace within tags, uses particular character encodings, sorts namespace references and eliminates redundant ones, removes XML and DOCTYPE declarations, and transforms relative URIs into absolute URIs. A simple example would be

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638-428: The page unique (for example, sorting by price or filtering by item color). The canonical can be in a different domain than a duplicate. With the help of canonical URLs, a search engine knows which link should be provided in a query result. A canonical link element can get used to define a canonical URL. In intranets , manual searching for information is predominant. In this case, canonical URLs can be defined in

667-523: The same legal value as a handwritten signature. An electronic signature, technically implemented based on XAdES has the status of an advanced electronic signature. This means that A resulting property of XAdES is that electronically signed documents can remain valid for long periods, even if underlying cryptographic algorithms are broken. However, courts are not obliged to accept XAdES-based electronic signatures as evidence in their proceedings; at least in EU, this

696-537: The same web content can cause problems for search engines - specifically in determining which URL should be shown in search results. Most search engines support the Canonical link element as a hint to which URL should be treated as the true version. As indicated by John Mueller of Google, having other directives in a page, like the robots noindex element can give search engines conflicting signals about how to handle canonicalization Example: All of these URLs point to

725-516: The signature and signed information, and perform transformations. Another core concept is canonicalization, that is to sign only the "essence", eliminating meaningless differences like whitespace and line endings. There are criticisms directed at the architecture of XML security in general, and at the suitability of XML canonicalization in particular as a front end to signing and encrypting XML data due to its complexity, inherent processing requirement, and poor performance characteristics. The argument

754-433: The signed data. Because the signed document's structure can be tampered with leading to "signature wrapping" attacks, the validation process should also cover XML document structure. Signed element and signature element should be selected using absolute XPath expression, not getElementByName methods. The creation of XML Signatures is substantially more complex than the creation of an ordinary digital signature because

783-419: The string " /./ " can be replaced by " / ". In the C standard library , the function realpath() performs this task. Other operations performed by this function to canonicalize filenames are the handling of /.. components referring to parent directories, simplification of sequences of multiple slashes, removal of trailing slashes, and the resolution of symbolic links . Canonicalization of filenames

812-487: The surrounding XML, was created. XML Signature is more flexible than other forms of digital signatures such as Pretty Good Privacy and Cryptographic Message Syntax , because it does not operate on binary data , but on the XML Infoset , allowing to work on subsets of the data (this is also possible with binary data in non-standard ways, for example encoding blocks of binary data in base64 ASCII), having various ways to bind

841-403: The way that the default canonicalization algorithm handles namespace declarations; frequently a signed XML document needs to be embedded in another document; in this case the original canonicalization algorithm will not yield the same result as if the document is treated alone. For this reason, the so-called Exclusive Canonicalization , which serializes XML namespace declarations independently of

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