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RFC4010-Use of the SEED Encryption Algorithm in Cryptographic Message Syntax (CMS)

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RFC4010-Use of the SEED Encryption Algorithm in Cryptographic Message Syntax (CMS)_电脑维修资料库

network working group j. parkrequest for comments: 4010 s. leecategory: standards track j. kimj. leekisafebruary 2005use of the seed encryption algorithmin cryptographic message syntax (cms)status of this memothis document specifies an internet standards track protocol for theinternet community, and requests discussion and suggestions forimprovements. please refer to the current edition of the internetofficial protocol standards (std 1) for the standardization stateand status of this protocol. distribution of this memo is unlimited.copyright noticecopyright (c) the internet society (2005).abstractthis document specifies the conventions for using the seed encryptionalgorithm for encryption with the cryptographic message syntax (cms).seed is added to the set of optional symmetric encryption algorithmsin cms by providing two classes of unique object identifiers (oids).one oid class defines the content encryption algorithms and the otherdefines the key encryption algorithms.1. introductionthis document specifies the conventions for using the seed encryptionalgorithm for encryption with the cryptographicmessage syntax (cms). the relevant object identifiers (oids)and processing steps are provided so that seed may be used in the cmsspecification (rfc 3852, rfc 3370) for content and key encryption.1.1. seedseed is a symmetric encryption algorithm developed by kisa (koreainformation security agency) and a group of experts since 1998. theinput/output block size and key length of seed is 128-bits. seed hasthe 16-round feistel structure. a 128-bit input is divided into two64-bit blocks and the right 64-bit block is an input to the roundfunction, with a 64-bit subkey generated from the key scheduling.seed is easily implemented in various software and hardware becauseit takes less memory to implement than other algorithms and generateskeys without degrading the security of the algorithm. in particular,it can be effectively adopted in a computing environment with arestricted resources, such as mobile devices and smart cards.seed is robust against known attacks including dc (differentialcryptanalysis), lc (linear cryptanalysis), and related key attacks.seed has gone through wide public scrutinizing procedures. it hasbeen evaluated and is considered cryptographically secure by credibleorganizations such as iso/iec jtc 1/sc 27 and japan cryptrec(cryptography research and evaluation committees).seed is a national industrial association standard and iswidely used in south korea for electronic commerce and financialservices operated on wired and wireless communications.1.2. terminologythe key words must, must not, required, should, should not,recommended, may, and optional in this document (in uppercase,as shown) are to be interpreted as described in .2. object identifiers for content and key encryptionthis section provides the oids and processing information necessaryfor seed to be used for content and key encryption in cms. seed isadded to the set of optional symmetric encryption algorithms in cmsby providing two classes of unique object identifiers (oids). oneoid class defines the content encryption algorithms and the otherdefines the key encryption algorithms. thus, a cms agent can applyseed either for content or key encryption by selecting thecorresponding object identifier, supplying the required parameter,and starting the program code.2.1. oids for content encryptionseed is added to the set of symmetric content encryption algorithmsdefined in . the seed content-encryption algorithm in cipherblock chaining (cbc) mode has the following object identifier:id-seedcbc object identifier ::={ iso(1) member-body(2) korea(410) kisa(200004)algorithm(1) seedcbc(4) }the algorithmidentifier parameters field must be present, and theparameters field must contain the value of initialization vector(iv):seedcbcparameter ::= seediv -- initialization vectorseediv ::= octet string (size(16))the plain text is padded according to section 6.3 of .2.2. oids for key encryptionthe key-wrap/unwrap procedures used to encrypt/decrypt a seedcontent-encryption key (cek) with a seed key-encryption key (kek) arespecified in section 3. generation and distribution of key-encryption keys are beyond the scope of this document.the seed key-encryption algorithm has the following objectidentifier:id-npki-app-cmsseed-wrap object identifier ::={ iso(1) member-body(2) korea(410) kisa(200004) npki-app(7)smime(1) alg(1) cmsseed-wrap(1) }the parameter associated with this object identifier must be absent,because the key wrapping procedure itself defines how and when to usean iv.3. key wrap algorithmseed key wrapping and unwrapping is done in conformance with the aeskey wrap algorithm .3.1. notation and definitionsthe following notation is used in the description of the key wrappingalgorithms:seed(k, w) encrypt w using the seed codebook with key kseed-1(k, w) decrypt w using the seed codebook with key kmsb(j, w) return the most significant j bits of wlsb(j, w) return the least significant j bits of wb1 ^ b2 the bitwise exclusive or (xor) of b1 and b2b1 | b2 concatenate b1 and b2k the key-encryption key kn the number of 64-bit key data blockss the number of steps in the wrapping process,s = 6np the ith plaintext key data blockc the ith ciphertext data blocka the 64-bit integrity check registerr an array of 64-bit registers wherei = 0, 1, 2, ..., na, r the contents of registers a and r afterencryption step t.iv the 64-bit initial value used during thewrapping process.in the key wrap algorithm, the concatenation function will be used toconcatenate 64-bit quantities to form the 128-bit input to the seedcodebook. the extraction functions will be used to split the 128-bitoutput from the seed codebook into two 64-bit quantities.3.2. seed key wrapkey wrapping with seed is identical to section 2.2.1 of with aes replaced by seed.the inputs to the key wrapping process are the kek and the plaintextto be wrapped. the plaintext consists of n 64-bit blocks containingthe key data being wrapped. the key wrapping process is describedbelow.inputs: plaintext, n 64-bit values {p<1>, p<2>, ..., p}, andkey, k (the kek).outputs: ciphertext, (n+1) 64-bit values {c<0>, c<1>, ..., c}.1) initialize variables.set a<0> to an initial value (see section 3.4)for i = 1 to nr<0> = p2) calculate intermediate values.for t = 1 to s, where s = 6na = msb(64, seed(k, a | r<1>)) ^ tfor i = 1 to n-1r = rr = lsb(64, seed(k, a | r<1>))3) output the results.set c<0> = afor i = 1 to nc = ran alternative description of the key wrap algorithm involvesindexing rather than shifting. this approach allows one to calculatethe wrapped key in place, avoiding the rotation in the previousdescription. this produces identical results and is more easilyimplemented in software.inputs: plaintext, n 64-bit values {p<1>, p<2>, ..., p}, andkey, k (the kek).outputs: ciphertext, (n+1) 64-bit values {c<0>, c<1>, ..., c}.1) initialize variables.set a = iv, an initial value (see section 3.4)for i = 1 to nr = p2) calculate intermediate values.for j = 0 to 5for i=1 to nb = seed(k, a | r)a = msb(64, b) ^ t where t = (n*j)+ir = lsb(64, b)3) output the results.set c<0> = afor i = 1 to nc = r3.3. seed key unwrapkey unwrapping with seed is identical to section 2.2.2 of ,with aes replaced by seed.the inputs to the unwrap process are the kek and (n+1) 64-bit blocksof ciphertext consisting of previously wrapped key. it returns nblocks of plaintext consisting of the n 64-bit blocks of thedecrypted key data.inputs: ciphertext, (n+1) 64-bit values {c<0>, c<1>, ..., c},and key, k (the kek).outputs: plaintext, n 64-bit values {p<1>, p<2>, ..., p}.1) initialize variables.set a = c<0> where s = 6nfor i = 1 to nr = c2) calculate the intermediate values.for t = s to 1a = msb(64, seed-1(k, ((a ^ t) | r))r<1> = lsb(64, seed-1(k, ((a^t) | r))for i = 2 to nr = r3) output the results.if a<0> is an appropriate initial value (see section 3.4),thenfor i = 1 to np = r<0>elsereturn an errorthe unwrap algorithm can also be specified as an index basedoperation, allowing the calculations to be carried out in place.again, this produces the same results as the register shiftingapproach.inputs: ciphertext, (n+1) 64-bit values {c<0>, c<1>, ..., c},and key, k (the kek).outputs: plaintext, n 64-bit values {p<0>, p<1>, ..., p}.1) initialize variables.set a = c<0>for i = 1 to nr = c2) compute intermediate values.for j = 5 to 0for i = n to 1b = seed-1(k, (a ^ t) | r) where t = n*j+ia = msb(64, b)r = lsb(64, b)3) output results.if a is an appropriate initial value (see section 3.4),thenfor i = 1 to np = relsereturn an error3.4. key data integrity -- the initial valuethe initial value (iv) refers to the value assigned to a<0> in thefirst step of the wrapping process. this value is used to obtain anintegrity check on the key data. in the final step of the unwrappingprocess, the recovered value of a<0> is compared to the expectedvalue of a<0>. if there is a match, the key is accepted as valid,and the unwrapping algorithm returns it. if there is not a match,then the key is rejected, and the unwrapping algorithm returns anerror.the exact properties achieved by this integrity check depend on thedefinition of the initial value. different applications may call forsomewhat different properties; for example, whether there is a needto determine the integrity of key data throughout its lifecycle orjust when it is unwrapped. this specification defines a defaultinitial value that supports the integrity of the key data during theperiod it is wrapped (in section 3.4.1). provision is also made tosupport alternative initial values (in section 3.4.2).3.4.1. default initial valuethe default initial value (iv) is defined to be the hexadecimalconstant:a<0> = iv = a6a6a6a6a6a6a6a6the use of a constant as the iv supports a strong integrity check onthe key data during the period that it is wrapped. if unwrappingproduces a<0> = a6a6a6a6a6a6a6a6, then the chance that the key datais corrupt is 2^-64. if unwrapping produces a<0> = any other value,then the unwrap must return an error and not return any key data.3.4.2. alternative initial valueswhen the key wrap is used as part of a larger key management protocolor system, the desired scope for data integrity may be more than justthe key data, and the desired duration may be more than just theperiod that it is wrapped. also, if the key data is not just a seedkey, it may not always be a multiple of 64 bits. alternativedefinitions of the initial value can be used to address suchproblems. according to rfc 3394 , nist will definealternative initial values in future key management publications asthey are needed. to accommodate a set of alternatives that mayevolve over time, non-application-specific key wrap implementationswill require some flexibility in the way the initial value is set andtested.4. smimecapabilities attributean s/mime client should announce the set of cryptographic functionsit supports by using the s/mime capabilities attribute. thisattribute provides a partial list of oids of cryptographic functionsand must be signed by the client. the functions' oids should belogically separated in functional categories and must be ordered withrespect to their preference.rfc 3851 , section 2.5.2 defines the smimecapabilitiessigned attribute (defined as a sequence of smimecapability sequences)to be used to specify a partial list of algorithms that the softwareannouncing the smimecapabilities can support.if an s/mime client is required to support symmetric encryption withseed, the capabilities attribute must contain the seed oid specifiedabove in the category of symmetric algorithms. the parameterassociated with this oid must be seedsmimecapability.seedsmimecapabilty ::= nullthe smimecapability sequence representing seed must be der-encoded asthe following hexadecimal strings:30 0c 06 08 2a 83 1a 8c 9a 44 01 04 05 00when a sending agent creates an encrypted message, it has to decidewhich type of encryption algorithm to use. in general, the decisionprocess involves information obtained from the capabilities listsincluded in messages received from the recipient, as well as otherinformation, such as private agreements, user preferences and legalrestrictions. if local policy requires the use of seed for symmetricencryption, then both the sending and receiving s/mime clients mustsupport it, and seed must be configured as the preferred symmetricalgorithm.5. security considerationsthis document specifies the use of seed for encrypting the content ofa cms message and for encrypting the symmetric key used to encryptthe content of a cms message, with the other mechanisms being thesame as the existing ones. therefore, the security considerationsdescribed in the cms specifications and the aes keywrap algorithm can be applied to this document. nosecurity problem has been found on seed .6. references6.1. normative references telecommunications technology association (tta), southkorea, 128-bit symmetric block cipher (seed), ttas.ko-12.0004, september, 1998 (in korean)http://www.tta.or.kr/english/new/main/index.htm housley, r., cryptographic message syntax (cms), rfc3852, july 2004. housley, r., cryptographic message syntax (cms)algorithms, rfc 3370, august 2002. ramsdell, b., secure/multipurpose internet mailextensions (s/mime) version 3.1 message specification,rfc 3851, july 2004. schaad, j. and r. housley, advanced encryption standard(aes) key wrap algorithm, rfc 3394, september 2002. bradner, s., key words for use in rfcs to indicaterequirement levels, bcp 14, rfc 2119, march 1997.6.2. informative references park, j., lee, s., kim, j., and j. lee, the seedencryption algorithm, rfc 4009, february 2005. iso/iec, iso/iec jtc1/sc 27 n 256r1, national bodycontributions on np 18033 encryption algorithms inresponse to document sc 27 n 2563, october, 2000 information-technology promotion agency (ipa), japan,cryptrec. seed evaluation report, february, 2002http://www.kisa.or.krappendix a. asn.1 moduleseedencryptionalgorithmincms{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)pkcs9(9) smime(16) modules(0) id-mod-cms-seed(24) }definitions implicit tags ::=beginid-seedcbc object identifier ::={ iso(1) member-body(2) korea(410) kisa(200004)algorithm(1) seedcbc(4) }-- initialization vector (iv)seedcbcparameter ::= seedivseediv ::= octet string (size(16))-- seed key wrap algorithm identifiers - parameter is absent.id-npki-app-cmsseed-wrap object identifier ::={ iso(1) member-body(2) korea(410) kisa(200004) npki-app(7)smime(1) alg(1) cmsseed-wrap(1) }-- seed s/mime capability parameterseedsmimecapability ::= nullendauthors' addressesjongwook parkkorea information security agency78, garak-dong, songpa-gu, seoul, 138-803republic of koreaphone: +82-2-405-5432fax : +82-2-405-5499email: khopri@kisa.or.krsungjae leekorea information security agencyphone: +82-2-405-5243fax : +82-2-405-5499email: sjlee@kisa.or.krjeeyeon kimkorea information security agencyphone: +82-2-405-5238fax : +82-2-405-5499email: jykim@kisa.or.krjaeil leekorea information security agencyphone: +82-2-405-5300fax : +82-2-405-5499email: jilee@kisa.or.krfull copyright statementcopyright (c) the internet society (2005).this document is subject to the rights, licenses and restrictionscontained in bcp 78, and except as set forth therein, the authorsretain all their rights.this document and the information contained herein are provided on anas is basis and the contributor, the organization he/she representsor is sponsored by (if any), the internet society and the internetengineering task force disclaim all warranties, express or implied,including but not limited to any warranty that the use of theinformation herein will not infringe any rights or any impliedwarranties of merchantability or fitness for a particular purpose.intellectual propertythe ietf takes no position regarding the validity or scope of anyintellectual property rights or other rights that might be claimed topertain to the implementation or use of the technology described inthis document or the extent to which any license under such rightsmight or might not be available; nor does it represent that it hasmade any independent effort to identify any such rights. informationon the ietf's procedures with respect to rights in ietf documents canbe found in bcp 78 and bcp 79.copies of ipr disclosures made to the ietf secretariat and anyassurances of licenses to be made available, or the result of anattempt made to obtain a general license or permission for the use ofsuch proprietary rights by implementers or users of thisspecification can be obtained from the ietf on-line ipr repository athttp://www.ietf.org/ipr.the ietf invites any interested party to bring to its attention anycopyrights, patents or patent applications, or other proprietaryrights that may cover technology that may be required to implementthis standard. please address the information to the ietf at ietf-ipr@ietf.org.acknowledgementfunding for the rfc editor function is currently provided by theinternet society.</t

 
 
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