XML Cryptography

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XML Cryptography

• Krishna Sattiraju
• CS 792 .NET

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Overview

• What is XML Encryption
• Methods for Encryption
• Storage of Encrypted Data
• Benefits of XML Secure Storage
• Types of XML Encryption

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XML Encryption

• Specification that defines how to encrypt data
• Used to encrypt data, keying information and
  algorithms

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Methods for encryption

• Using Symmetric Encryption
• Combination of Symmetric and Asymmetric
  Encryption
• X.509 Certificates

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Storage of Encrypted Data

• Whole element is replaced with an element
  named ltEncryptedDatagt
• Only the data in the element is replaced and its
  name remains readable in the document

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XML Document Code
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Encrypted Code
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Asymmetric XML Encryption and Decryption

• Select XML Element
• Encrypt element
• Encrypt Session Key
• Create Encrypted Data element
• Replace Original element
• Select Encrypted Data element
• Decrypt Session Key
• Decrypt Cipher Data using unencrypted symmetric
• Replace the Encrypted Data Element

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Name Spaces

• System. XML
• System.Security. Cryptography
• System.Security.Cryptography.xml

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Benefits of XML Secure Storage

• XML Is Structured Format
• Allows for secure storage of documents
• Provides granularity
• Leverages Existing technologies

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XML Encryption

• Encrypted data is maintained.
• All information needed to decrypt a document is
  contained within the document.
• Session can be secured on the document level and
  shared between multiple parties.
• Sensitive data is easily interchanged between
  applications.

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XML Encryption of Element
lt?xml version'1.0'?gt ltPaymentInfo
xmlns'http//example.org/paymentv2'gt ltNamegtJohn
Smith lt/Namegt ltEncryptedData Type'http//www.w3.
org/2001/04/xmlencElement' xmlns'http//www.w3.o
rg/2001/04/xmlenc'gt ltCipherDatagt
ltCipherValuegtA23B45C56 lt/CipherValuegt
lt/CipherDatagt lt/EncryptedDatagt lt/PaymentInfogt
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XML Encryption using Content
lt?xml version'1.0'?gt ltPaymentInfo
xmlns'http//example.org/paymentv2'gt ltNamegtJohn
Smith lt/Namegt ltCreditCard Limit'5,000'
Currency'USD'gt ltEncryptedData
xmlns'http//www.w3.org/2001/04/xmlenc'
Type'http//www.w3.org/2001/04/xmlencContent'gt
ltCipherDatagt ltCipherValuegtA23B45C56 lt/CipherValue
gt lt/CipherDatagt lt/EncryptedDatagt lt/CreditCardgt
lt/PaymentInfogt
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Encrypting XML Content (Character Data)
lt?xml version'1.0'?gt ltPaymentInfo
xmlns'http//example.org/paymentv2'gt ltNamegtJohn
Smithlt/Namegt ltCreditCard Limit'5,000'
Currency'USD'gt ltNumbergt ltEncryptedData
xmlns'http//www.w3.org/2001/04/xmlenc'
Type'http//www.w3.org/2001/04/xmlencContent'gt
ltCipherDatagt ltCipherValuegtA23B45C56lt/CipherValuegt
lt/CipherDatagt lt/EncryptedDatagt lt/Numbergt
ltIssuergtExample Banklt/Issuergt ltExpirationgt04/02lt/
Expirationgt lt/CreditCardgt lt/PaymentInfogt
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XML Encryption in WS-Security
ltenvEnvelope xmlnsenv"http//www.w3.org/2
001/12/soap-envelope"
xmlnsxenc"http//www.w3.org/2001/04/xmlenc"gt
ltenvHeadergt ltwsseSecurity
xmlnswsse"http//schemas.xmlsoap.org/ws/200
2/04/secext"gt ltxencReferenceListgt
ltxencDataReference URI"encryptedID"/gt
lt/xencReferenceListgt
lt/wsseSecuritygt lt/envHeadergt ltenvBodygt
ltxencEncryptedData Id"encryptedID"gt
ltxencCipherDatagt
ltxencCipherValuegt...lt/xencCipherValuegt
lt/xencCipherDatagt lt/xencEncryptedDatagt
lt/envBodygt lt/envEnvelopegt
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XML Encryption w/ Digital Certificate
ltEncryptedData xmlns"http//www.w3.org/2001/04/xm
lenc"
Type"http//www.w3.org/2001/04/xmlencElement"gt lt
EncryptionMethod Algorithm"http//www.
w3.org/2001/04/xmlenctripledes-cbc"/gt ltKeyInfo
xmlns"http//www.w3.org/2000/09/xmldsig"gt
ltEncryptedKey xmlns"http//www.w3.org/2001/04/xml
enc"gt ltEncryptionMethod Algorithm"http//www.
w3.org/2001/04/xmlencrsa-oaep-mgf1p"/gt
ltKeyInfo xmlns"http//www.w3.org/2000/09/xmldsig
"gt ltKeyNamegtrsakey.pemlt/KeyNamegt
lt/KeyInfogt ltCipherDatagt
ltCipherValuegtIPiEu9NvEsGyvV . . .lt/CipherValuegt
lt/CipherDatagt lt/EncryptedKeygt lt/KeyInfogt ltCiphe
rDatagtltCipherValuegtxrfPSABEI8 . .
.lt/CipherValuegt lt/CipherDatagtlt/EncryptedDatagt
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XML Signing AND XML Encryption

• Order of Cryptographic operations matters
• Signing and Encrypting
• Encrypting and Signing
• Change of the order while Decrypting - Danger

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References

• XML Encryption by By Derek Smyth
  http//dotnetslackers.com/articles/xml/XMLEncrypti
  on.aspx
• XML Encryption Syntax and Processing By Takeshi
  Imamura , Blair Dillaway, Ed Simon
• http//www.ibm.com/developerworks/xml/library/x-en
  crypt2/
• http//www.devx.com/dotnet/Article/21564

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Thank You!!!