Public Key Infrastructures

Transcription

1 Public Key Infrastructures How to store private keys? Chapter 6 Private Keys Cryptography and Computeralgebra Vangelis Karatsiolis Alexander Wiesmaier 1 2 Personal Security Environment (PSE) Realisation of PSEs : Tokens Secure storing of private keys Private keys are stored in PSEs in Software in Hardware PKCS#12 Java KeyStore Application specific (e.g. Netscape) USB-Token Smartcard Hardware Security Module (HSM) 3 4

2 Token properties PKCS#12 Compatibility Portability Availability Access protection Software based PSE Format for secure transport and storing Most typical format for software PSEs Available at: PKCS#12: Modes PKCS#12: Structure AuthenticatedSafe Public Key Privacy Mode: Encryption with a symmetric key. This symmetric key is encrypted with the public key of the receiver. Password Privacy Mode: Encryption with one symmetric key, which is derived from a password. Public Key Integrity Mode: Signed with a private key. The receiver can verify the message. Password Integrity Mode: A MAC is calculated which can be verified by the receiver. ContentInfo Plain data Encrypted data Enveloped data 7 8

3 Example Personal nformation Exchange Password: Java Keystores Implementation of the KeyStore Class Two types: JKS Proprietary algorithms Weak encryption JCEKS Standard algorithms Strong encryption Part of the JCE (Java Cryptography Extensions) Since Java 1.4 KeyStore example keytool -genkey -alias test -keyalg RSA -keysize keypass storepass keystore test.ks Run:../Certificates/keytool.bat Easy Administration with keytool 11 12

4 Application specific Private key import in Firefox Examples: Mozilla Windows Private key access in Firefox Private key import in Windows 15 16

5 Private key access in Windows Application specific Netscape Family Mozilla, Firefox, Thunderbird, SeaMonkey Through Software Security Module The standard implementation is proprietary The format for the import is PKCS#12 Windows Internet Explorer, Outlook/Express The standard implementation is proprietary Through Cryptographic Service Provider The format for the import is PKCS# Hardware Security Module Hardware Security Module Protect the keys against Mechanical attacks Secure storage and use of keys (Pseudo)random number generation Key pair generation Calculation of digital signatures Key archiving Temperature attacks Manipulation of the voltage Chemical attacks The keys are destroyed in case of danger Acceleration for cryptographic schemes 19 20

6 Hardware Security Module Network Attached HSM But Keys can be accidentally destroyed e.g. due to mechanical influence during transport Speed Availability Robustness Smartcards Access over PKCS#11 Interface to the card Secure key storing and use Key pair generation (not all) Calculation of digital signatures Decryption Support functions like: Change PIN, Sign, Decrypt, Write certificate But: Some functions are not supported (e.g. change PUK) Possibly many libraries are needed for supporting different cards and readers. Available at:

7 PKCS#15 Specifies the structure of the card in the card Every directory in the card is an application Structure PKCS#15 MasterFile Pointers to cryptographic objekts (ODF) PrivateKey PublicKey Descriptor DF(PKCS#15) Userdata EF (DIR) Further DFs/EFs Certificate There is a a newer specification based on it: ISO ODF PrKDF CDF ADF TokenInfo Available at: Pointer to PrivateKey Data, Certificate Data, Authentication Data (PIN) and Token Information (Serial number) E4 NetKey (TeleSec) E4 evaluated (according to ITSEC) Global files (serial number, etc.) SigG application Pre-keyd with one key-pair according to SigG (Signature Act) NetKey application 3 key pairs (pre-keyed) Null-PIN scheme (patented) Java Cards No filesystem but applets JCRE (Java Card Runtime Environment) manages: the resources of the card the communication with the outside world the execution of the applets controls: the compliance with the security limitations 27 28

8 Java Cards Like normal Java code but not: Long, double, float Characters and strings Multidimensional arrays Threads Object serialisation und cloning Dynamic loading of classes (like drivers) Security Manager Garbage Collector not always present Examples Of secure signature-creation devices Secure signature-creation devices Life cycle of private keys Life cycle of private keys Backup Backup Storing Recovery Storing Recovery Transport Transport Use start state state Use appropriate parameters secure random number generator Destruction end state Destruction shielding against eavesdropping 31 32

9 Life cycle of private keys Life cycle of private keys Backup Backup Storing Recovery Storing Recovery Transport Transport persistent storing correct receiver Use deletion from the generator Use guaranteed delivery Destruction appropriate access protection Destruction appropriate transport security mechanisms Life cycle of private keys Life cycle of private keys Backup Backup Storing Recovery Storing Recovery Transport Transport easy for the authorised users unrecoverable Use Destruction impossible for the unauthorised users protection of the private key 35 Use Destruction easy for authorised users impossible for unauthorised users 36

10 Life cycle of private keys Life cycle of private keys Backup Backup Storing Recovery Storing Recovery Transport Transport persistent storing correct reestablishment Use only for certain keys Use easy for authorised users Destruction appropriate access protection 37 Destruction impossible for unauthorised users 38 User generates key Example 1: User generates key (PGP) 39 40

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12 45 46 Storing 47 48

13 Transport Transport Transport Use File contents../certificates/test User.cxt 51 52

14 Use Destruction Destruction Destruction 55 56

15 Backup Backup Backup Backup 59 60

16 Recovery Recovery Recovery Trust center generates key Example 2: Trust center generates key (X.509) TUDCard 63 64

17 Storing The manufacturer creates the keys Contains the private key A file exists that holds the private key. input Security condition: PSO (Perform Security Operation) after PIN has been correctly given. output Transport Use By snail mail First Use detection Null-PIN technique 67 68

18 Use Use Set PIN See PUK Download certificate PIN-Entry necessary for PSO Destruction Backup Physical destruction of the card. high temperature, etc Every key is stored in a PKCS#12 file input 71 output 72

19 User generates key Generate Example 3: keytool -genkey -keyalg RSA -keystore keystore.ks -alias myalias User generates key (X.509) The user generates its own private key Store Transport keytool -genkey -keyalg RSA -keystore keystore.ks -alias myalias The key is already at the client side

20 Use In order to use the private key, the public key is certified by a CA. Thawte example

21 81 82 Hi! Please use your browser to go to the following URL: Once you have connected successfully to the above address, you must copy and paste the "probe" and "ping" values below into the appropriate text boxes: Probe: value Ping: value You should save this message until you have completed the enrollment process, just in case. But you MUST go to the above URL within 24 hours, or we will delete your request information and you'll have to start over! If you have problems completing the above please contact our support team by going to the following URL: Regards, The thawte team thawte Certification 83 84

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23 address 91 92

24 93 94 keytool -certreq -keystore keystore.ks -file csr.txt -alias myalias BEGIN NEW CERTIFICATE REQUEST----- MIIBrDCCARUCAQwbDELMAkGA1UEBhMCREUxDjAMBgNVB TBUhlc3NlMRIwEAYDVQQHEwlEYXJtN57qbnyAfAAAAAAA c3rhzhqxddkbgnvata1rvrdemmaoga1uecxmdq0rdmr wgwydvqqdexrwy5nzwxpcyblyxjhn57qbnyafaaaaaaa dhnpb2xpcznzanbqhkig9w0baqefaaobjqawgykcgyearoj ITHFBR5orQ9dB4qkP/gMhS1hCNiowdM2CrJINiowdM2CCCCE +Qrzut77pzzjlEBLQeeMC0Q88LF8tTJfFoUKdGni/PAAiOPHxv NXFFH0YZs4/P7gXMAX+9eEgGNiowdM2CrJINiowdM2CCCCE jl2ig7pyqlkggwibvxyqmex2tkk9tkwqcvfjl6bktjiijermgoly i79dk3cdwx26z8caweaaaaaniowdm2crjiniowdm2cccceee MA0GCSqGSIb3DEBBAUAAGBAIvbaheW+lVaDdRN57qbnyAf3 qqxd2gcjmbccco8v3tn9zc4mseniowdm2crjiniowdm2cccc pxxtfqg4uqo0urjiniowdm2ctrpzletorjntoxxirlhp9+lln XnER43nYvcLZ/QIChlfIX6KiPrJINiowdM2CrJINiowdM2CCCC Elr81bvYRq6G/bGxrz4K55c17UIqPtlGN7yQEDxYZ5e END NEW CERTIFICATE REQUEST

25 97 98 The user receives a URL that contains the certificate inside a PKCS#7 structure

26 Destruction keytool -import -file test.crt -alias myalias -trustcacerts -keystore keystore.ks Backup Recovery A simple copy of the file to: a CD a USB stick an external hard disc or similar Recovery from the copy location. Password is needed. The password may be changed