net.java.otr4j.crypto

Class SM

java.lang.Object

net.java.otr4j.crypto.SM

public class SM
extends Object

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SM.SMException
static class	SM.SMState

Field Summary

Fields

Modifier and Type	Field and Description
static int	EXPECT1
static int	EXPECT2
static int	EXPECT3
static int	EXPECT4
static int	EXPECT5
static byte[]	GENERATOR_S
static int	MOD_LEN_BITS
static int	MOD_LEN_BYTES
static BigInteger	MODULUS_MINUS_2
static BigInteger	MODULUS_S
static int	MSG1_LEN
static int	MSG2_LEN
static int	MSG3_LEN
static int	MSG4_LEN
static BigInteger	ORDER_S
static int	PROG_CHEATED
static int	PROG_FAILED
static int	PROG_OK
static int	PROG_SUCCEEDED

Constructor Summary

Constructors

Constructor and Description
SM()

Method Summary

Modifier and Type	Method and Description
static int	checkEqualCoords(BigInteger c, BigInteger d1, BigInteger d2, BigInteger p, BigInteger q, SM.SMState state, int version) Verify a proof of knowledge of coordinates with first components being equal
static int	checkEqualLogs(BigInteger c, BigInteger d, BigInteger r, SM.SMState state, int version) Verify a proof of knowledge of logs with exponents being equal
static boolean	checkExpon(BigInteger x) Check that an BigInteger is in the right range to be a (non-zero) exponent.
static boolean	checkGroupElem(BigInteger g) Check that an BigInteger is in the right range to be a (non-unit) group element.
static int	checkKnowLog(BigInteger c, BigInteger d, BigInteger g, BigInteger x, int version) Verify a proof of knowledge of a discrete logarithm.
static BigInteger	hash(int version, BigInteger a, BigInteger b) Hash one or two BigIntegers.
static void	main(String[] args)
static BigInteger[]	proofEqualCoords(SM.SMState state, BigInteger r, int version) Proof of knowledge of coordinates with first components being equal
static BigInteger[]	proofEqualLogs(SM.SMState state, int version) Proof of knowledge of logs with exponents being equal
static BigInteger[]	proofKnowLog(BigInteger g, BigInteger x, int version) Proof of knowledge of a discrete logarithm.
static BigInteger	randomExponent() Generate a random exponent
static byte[]	serialize(BigInteger[] ints)
static byte[]	step1(SM.SMState astate, byte[] secret) Create first message in SMP exchange.
static void	step2a(SM.SMState bstate, byte[] input, int received_question) Receive the first message in SMP exchange, which was generated by step1.
static byte[]	step2b(SM.SMState bstate, byte[] secret) Create second message in SMP exchange.
static byte[]	step3(SM.SMState astate, byte[] input) Create third message in SMP exchange.
static byte[]	step4(SM.SMState bstate, byte[] input) Create final message in SMP exchange.
static void	step5(SM.SMState astate, byte[] input) Receives the final SMP message, which was generated in otrl_sm_step.
static BigInteger[]	unserialize(byte[] bytes)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

EXPECT1

public static final int EXPECT1

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Constant Field Values

EXPECT2

public static final int EXPECT2

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EXPECT3

public static final int EXPECT3

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EXPECT4

public static final int EXPECT4

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EXPECT5

public static final int EXPECT5

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PROG_OK

public static final int PROG_OK

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PROG_CHEATED

public static final int PROG_CHEATED

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PROG_FAILED

public static final int PROG_FAILED

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PROG_SUCCEEDED

public static final int PROG_SUCCEEDED

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MSG1_LEN

public static final int MSG1_LEN

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MSG2_LEN

public static final int MSG2_LEN

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MSG3_LEN

public static final int MSG3_LEN

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MSG4_LEN

public static final int MSG4_LEN

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MODULUS_S

public static final BigInteger MODULUS_S

MODULUS_MINUS_2

public static final BigInteger MODULUS_MINUS_2

ORDER_S

public static final BigInteger ORDER_S

GENERATOR_S

public static final byte[] GENERATOR_S

MOD_LEN_BITS

public static final int MOD_LEN_BITS

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MOD_LEN_BYTES

public static final int MOD_LEN_BYTES

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Constructor Detail

SM

public SM()

Method Detail

randomExponent

public static BigInteger randomExponent()

Generate a random exponent

Returns:

the generated random exponent.

hash

public static BigInteger hash(int version,
                              BigInteger a,
                              BigInteger b)
                       throws SM.SMException

Hash one or two BigIntegers. To hash only one BigInteger, b may be set to NULL.

Parameters:

version - the prefix to use

a - The 1st BigInteger to hash.

b - The 2nd BigInteger to hash.

Returns:

the BigInteger for the resulting hash value.

Throws:

SM.SMException - when the SHA-256 algorithm is missing or when the biginteger can't be serialized.

serialize

public static byte[] serialize(BigInteger[] ints)
                        throws SM.SMException

Throws:

SM.SMException

unserialize

public static BigInteger[] unserialize(byte[] bytes)
                                throws SM.SMException

Throws:

SM.SMException

checkGroupElem

public static boolean checkGroupElem(BigInteger g)

Check that an BigInteger is in the right range to be a (non-unit) group element.

Parameters:

g - the BigInteger to check.

Returns:

true if the BigInteger is in the right range, false otherwise.

checkExpon

public static boolean checkExpon(BigInteger x)

Check that an BigInteger is in the right range to be a (non-zero) exponent.

Parameters:

x - The BigInteger to check.

Returns:

true if the BigInteger is in the right range, false otherwise.

proofKnowLog

public static BigInteger[] proofKnowLog(BigInteger g,
                                        BigInteger x,
                                        int version)
                                 throws SM.SMException

Proof of knowledge of a discrete logarithm.

Parameters:

g - the group generator

x - the secret information

version - the prefix to use for the hashing function

Returns:

c and d.

Throws:

SM.SMException - when c and d could not be calculated

checkKnowLog

public static int checkKnowLog(BigInteger c,
                               BigInteger d,
                               BigInteger g,
                               BigInteger x,
                               int version)
                        throws SM.SMException

Verify a proof of knowledge of a discrete logarithm. Checks that c = h(g^d x^c)

Parameters:

c - c from remote party

d - d from remote party

g - the group generator

x - our secret information

version - the prefix to use

Returns:

-1, 0 or 1 as our locally calculated value of c is numerically less than, equal to, or greater than c.

Throws:

SM.SMException - when something goes wrong

proofEqualCoords

public static BigInteger[] proofEqualCoords(SM.SMState state,
                                            BigInteger r,
                                            int version)
                                     throws SM.SMException

Proof of knowledge of coordinates with first components being equal

Parameters:

state - MVN_PASS_JAVADOC_INSPECTION

r - MVN_PASS_JAVADOC_INSPECTION

version - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

checkEqualCoords

public static int checkEqualCoords(BigInteger c,
                                   BigInteger d1,
                                   BigInteger d2,
                                   BigInteger p,
                                   BigInteger q,
                                   SM.SMState state,
                                   int version)
                            throws SM.SMException

Verify a proof of knowledge of coordinates with first components being equal

Parameters:

c - MVN_PASS_JAVADOC_INSPECTION

d1 - MVN_PASS_JAVADOC_INSPECTION

d2 - MVN_PASS_JAVADOC_INSPECTION

p - MVN_PASS_JAVADOC_INSPECTION

q - MVN_PASS_JAVADOC_INSPECTION

state - MVN_PASS_JAVADOC_INSPECTION

version - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

proofEqualLogs

public static BigInteger[] proofEqualLogs(SM.SMState state,
                                          int version)
                                   throws SM.SMException

Proof of knowledge of logs with exponents being equal

Parameters:

state - MVN_PASS_JAVADOC_INSPECTION

version - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

checkEqualLogs

public static int checkEqualLogs(BigInteger c,
                                 BigInteger d,
                                 BigInteger r,
                                 SM.SMState state,
                                 int version)
                          throws SM.SMException

Verify a proof of knowledge of logs with exponents being equal

Parameters:

c - MVN_PASS_JAVADOC_INSPECTION

d - MVN_PASS_JAVADOC_INSPECTION

r - MVN_PASS_JAVADOC_INSPECTION

state - MVN_PASS_JAVADOC_INSPECTION

version - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

step1

public static byte[] step1(SM.SMState astate,
                           byte[] secret)
                    throws SM.SMException

Create first message in SMP exchange. Input is Alice's secret value which this protocol aims to compare to Bob's. The return value is a serialized BigInteger array whose elements correspond to the following: [0] = g2a, Alice's half of DH exchange to determine g2 [1] = c2, [2] = d2, Alice's ZK proof of knowledge of g2a exponent [3] = g3a, Alice's half of DH exchange to determine g3 [4] = c3, [5] = d3, Alice's ZK proof of knowledge of g3a exponent

Parameters:

astate - MVN_PASS_JAVADOC_INSPECTION

secret - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

step2a

public static void step2a(SM.SMState bstate,
                          byte[] input,
                          int received_question)
                   throws SM.SMException

Receive the first message in SMP exchange, which was generated by step1. Input is saved until the user inputs their secret information. No output.

Parameters:

bstate - MVN_PASS_JAVADOC_INSPECTION

input - MVN_PASS_JAVADOC_INSPECTION

received_question - MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

step2b

public static byte[] step2b(SM.SMState bstate,
                            byte[] secret)
                     throws SM.SMException

Create second message in SMP exchange. Input is Bob's secret value. Information from earlier steps in the exchange is taken from Bob's state. Output is a serialized mpi array whose elements correspond to the following: [0] = g2b, Bob's half of DH exchange to determine g2 [1] = c2, [2] = d2, Bob's ZK proof of knowledge of g2b exponent [3] = g3b, Bob's half of DH exchange to determine g3 [4] = c3, [5] = d3, Bob's ZK proof of knowledge of g3b exponent [6] = pb, [7] = qb, Bob's halves of the (Pa/Pb) and (Qa/Qb) values [8] = cp, [9] = d5, [10] = d6, Bob's ZK proof that pb, qb formed correctly

Parameters:

bstate - MVN_PASS_JAVADOC_INSPECTION

secret - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

step3

public static byte[] step3(SM.SMState astate,
                           byte[] input)
                    throws SM.SMException

Create third message in SMP exchange. Input is a message generated by otrl_sm_step2b. Output is a serialized mpi array whose elements correspond to the following: [0] = pa, [1] = qa, Alice's halves of the (Pa/Pb) and (Qa/Qb) values [2] = cp, [3] = d5, [4] = d6, Alice's ZK proof that pa, qa formed correctly [5] = ra, calculated as (Qa/Qb)^x3 where x3 is the exponent used in g3a [6] = cr, [7] = d7, Alice's ZK proof that ra is formed correctly

Parameters:

astate - MVN_PASS_JAVADOC_INSPECTION

input - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

step4

public static byte[] step4(SM.SMState bstate,
                           byte[] input)
                    throws SM.SMException

Create final message in SMP exchange. Input is a message generated by otrl_sm_step3. Output is a serialized mpi array whose elements correspond to the following: [0] = rb, calculated as (Qa/Qb)^x3 where x3 is the exponent used in g3b [1] = cr, [2] = d7, Bob's ZK proof that rb is formed correctly This method also checks if Alice and Bob's secrets were the same. If so, it returns NO_ERROR. If the secrets differ, an INV_VALUE error is returned instead.

Parameters:

bstate - MVN_PASS_JAVADOC_INSPECTION

input - MVN_PASS_JAVADOC_INSPECTION

Returns:

MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

step5

public static void step5(SM.SMState astate,
                         byte[] input)
                  throws SM.SMException

Receives the final SMP message, which was generated in otrl_sm_step. This method checks if Alice and Bob's secrets were the same. If so, it returns NO_ERROR. If the secrets differ, an INV_VALUE error is returned instead.

Parameters:

astate - MVN_PASS_JAVADOC_INSPECTION

input - MVN_PASS_JAVADOC_INSPECTION

Throws:

SM.SMException - MVN_PASS_JAVADOC_INSPECTION

main

public static void main(String[] args)
                 throws SM.SMException

Throws:

SM.SMException