More separation of the code

4 files changed, 147 insertions, 127 deletions

diff --git a/rsa/__init__.py b/rsa/__init__.py
index 3aef6d8..5fc5768 100755
--- a/rsa/__init__.py
+++ b/rsa/__init__.py
@@ -1,7 +1,7 @@
 """RSA module
 
-Module for calculating large primes, and RSA encryption, decryption,
-signing and verification. Includes generating public and private keys.
+Module for calculating large primes, and RSA encryption, decryption, signing
+and verification. Includes generating public and private keys.
 
 WARNING: this implementation does not use random padding, compression of the
 cleartext input to prevent repetitions, or other common security improvements.
@@ -13,133 +13,12 @@ __author__ = "Sybren Stuvel, Marloes de Boer, Ivo Tamboer, and Barry Mead"
 __date__ = "2010-02-08"
 __version__ = '2.1-beta0'
 
-import math
-import types
-
 import rsa.prime
 import rsa.transform
+import rsa.common
 
-def bit_size(number):
-    """Returns the number of bits required to hold a specific long number"""
-
-    return int(math.ceil(math.log(number,2)))
-
-
-def extended_gcd(a, b):
-    """Returns a tuple (r, i, j) such that r = gcd(a, b) = ia + jb
-    """
-    # r = gcd(a,b) i = multiplicitive inverse of a mod b
-    #      or      j = multiplicitive inverse of b mod a
-    # Neg return values for i or j are made positive mod b or a respectively
-    # Iterateive Version is faster and uses much less stack space
-    x = 0
-    y = 1
-    lx = 1
-    ly = 0
-    oa = a                             #Remember original a/b to remove 
-    ob = b                             #negative values from return results
-    while b != 0:
-        q = long(a/b)
-        (a, b)  = (b, a % b)
-        (x, lx) = ((lx - (q * x)),x)
-        (y, ly) = ((ly - (q * y)),y)
-    if (lx < 0): lx += ob              #If neg wrap modulo orignal b
-    if (ly < 0): ly += oa              #If neg wrap modulo orignal a
-    return (a, lx, ly)                 #Return only positive values
-
-def find_p_q(nbits):
-    """Returns a tuple of two different primes of nbits bits"""
-    pbits = nbits + (nbits/16)  #Make sure that p and q aren't too close
-    qbits = nbits - (nbits/16)  #or the factoring programs can factor n
-    p = rsa.prime.getprime(pbits)
-    while True:
-        q = rsa.prime.getprime(qbits)
-
-        #Make sure p and q are different.
-        if q != p: break
-
-    return (p, q)
-
-
-
-# Main function: calculate encryption and decryption keys
-def calculate_keys(p, q, nbits):
-    """Calculates an encryption and a decryption key for p and q, and
-    returns them as a tuple (e, d)"""
-
-    n = p * q
-    phi_n = (p-1) * (q-1)
-
-    while True:
-        # Make sure e has enough bits so we ensure "wrapping" through
-        # modulo n
-        e = max(65537, rsa.prime.getprime(nbits/4))
-        if rsa.prime.are_relatively_prime(e, n) and rsa.prime.are_relatively_prime(e, phi_n):
-            break
-
-    (d, i, j) = extended_gcd(e, phi_n)
-
-    if not d == 1:
-        raise Exception("e (%d) and phi_n (%d) are not relatively prime" % (e, phi_n))
-    if (i < 0):
-        raise Exception("New extended_gcd shouldn't return negative values")
-    if not (e * i) % phi_n == 1:
-        raise Exception("e (%d) and i (%d) are not mult. inv. modulo phi_n (%d)" % (e, i, phi_n))
-
-    return (e, i)
-
-
-def gen_keys(nbits):
-    """Generate RSA keys of nbits bits. Returns (p, q, e, d).
-
-    Note: this can take a long time, depending on the key size.
-    """
-
-    (p, q) = find_p_q(nbits)
-    (e, d) = calculate_keys(p, q, nbits)
-
-    return (p, q, e, d)
-
-def newkeys(nbits):
-    """Generates public and private keys, and returns them as (pub,
-    priv).
-
-    The public key consists of a dict {e: ..., , n: ....). The private
-    key consists of a dict {d: ...., p: ...., q: ....).
-    """
-    nbits = max(9,nbits)           # Don't let nbits go below 9 bits
-    (p, q, e, d) = gen_keys(nbits)
-
-    return ( {'e': e, 'n': p*q}, {'d': d, 'p': p, 'q': q} )
-
-def encrypt_int(message, ekey, n):
-    """Encrypts a message using encryption key 'ekey', working modulo n"""
-
-    if type(message) is types.IntType:
-        message = long(message)
-
-    if not type(message) is types.LongType:
-        raise TypeError("You must pass a long or int")
-
-    if message < 0 or message > n:
-        raise OverflowError("The message is too long")
-
-    #Note: Bit exponents start at zero (bit counts start at 1) this is correct
-    safebit = bit_size(n) - 2                   #compute safe bit (MSB - 1)
-    message += (1 << safebit)                   #add safebit to ensure folding
-
-    return pow(message, ekey, n)
-
-def decrypt_int(cyphertext, dkey, n):
-    """Decrypts a cypher text using the decryption key 'dkey', working
-    modulo n"""
-
-    message = pow(cyphertext, dkey, n)
-
-    safebit = bit_size(n) - 2                   #compute safe bit (MSB - 1)
-    message -= (1 << safebit)                   #remove safebit before decode
-
-    return message
+from rsa.keygen import newkeys
+from rsa.core import encrypt_int, decrypt_int
 
 def encode64chops(chops):
     """base64encodes chops and combines them into a ',' delimited string"""
@@ -186,7 +65,7 @@ def chopstring(message, key, n, int_op):
     mbits = msglen * 8
 
     # Set aside 2 bits so setting of safebit won't overflow modulo n.
-    nbits = bit_size(n) - 2             # leave room for safebit
+    nbits = rsa.common.bit_size(n) - 2             # leave room for safebit
     nbytes = nbits / 8
     blocks = msglen / nbytes
 
diff --git a/rsa/common.py b/rsa/common.py
new file mode 100644
index 0000000..d00a44d
--- /dev/null
+++ b/rsa/common.py
@@ -0,0 +1,9 @@
+'''Common functionality shared by several modules.'''
+
+import math
+
+def bit_size(number):
+    """Returns the number of bits required to hold a specific long number"""
+
+    return int(math.ceil(math.log(number,2)))
+
diff --git a/rsa/core.py b/rsa/core.py
new file mode 100644
index 0000000..f42801c
--- /dev/null
+++ b/rsa/core.py
@@ -0,0 +1,39 @@
+'''Core mathematical operations.
+
+This is the actual core RSA implementation, which is only defined
+mathematically on integers.
+'''
+
+import types
+
+import rsa.common
+
+def encrypt_int(message, ekey, n):
+    """Encrypts a message using encryption key 'ekey', working modulo n"""
+
+    if type(message) is types.IntType:
+        message = long(message)
+
+    if not type(message) is types.LongType:
+        raise TypeError("You must pass a long or int")
+
+    if message < 0 or message > n:
+        raise OverflowError("The message is too long")
+
+    #Note: Bit exponents start at zero (bit counts start at 1) this is correct
+    safebit = rsa.common.bit_size(n) - 2                   #compute safe bit (MSB - 1)
+    message += (1 << safebit)                   #add safebit to ensure folding
+
+    return pow(message, ekey, n)
+
+def decrypt_int(cyphertext, dkey, n):
+    """Decrypts a cypher text using the decryption key 'dkey', working
+    modulo n"""
+
+    message = pow(cyphertext, dkey, n)
+
+    safebit = rsa.common.bit_size(n) - 2                   #compute safe bit (MSB - 1)
+    message -= (1 << safebit)                   #remove safebit before decode
+
+    return message
+
diff --git a/rsa/keygen.py b/rsa/keygen.py
new file mode 100644
index 0000000..7a7cdb6
--- /dev/null
+++ b/rsa/keygen.py
@@ -0,0 +1,93 @@
+'''RSA key generation code.'''
+
+import rsa.prime
+
+def extended_gcd(a, b):
+    """Returns a tuple (r, i, j) such that r = gcd(a, b) = ia + jb
+    """
+    # r = gcd(a,b) i = multiplicitive inverse of a mod b
+    #      or      j = multiplicitive inverse of b mod a
+    # Neg return values for i or j are made positive mod b or a respectively
+    # Iterateive Version is faster and uses much less stack space
+    x = 0
+    y = 1
+    lx = 1
+    ly = 0
+    oa = a                             #Remember original a/b to remove 
+    ob = b                             #negative values from return results
+    while b != 0:
+        q = long(a/b)
+        (a, b)  = (b, a % b)
+        (x, lx) = ((lx - (q * x)),x)
+        (y, ly) = ((ly - (q * y)),y)
+    if (lx < 0): lx += ob              #If neg wrap modulo orignal b
+    if (ly < 0): ly += oa              #If neg wrap modulo orignal a
+    return (a, lx, ly)                 #Return only positive values
+
+
+
+def find_p_q(nbits):
+    """Returns a tuple of two different primes of nbits bits"""
+    pbits = nbits + (nbits/16)  #Make sure that p and q aren't too close
+    qbits = nbits - (nbits/16)  #or the factoring programs can factor n
+    p = rsa.prime.getprime(pbits)
+    while True:
+        q = rsa.prime.getprime(qbits)
+
+        #Make sure p and q are different.
+        if q != p: break
+
+    return (p, q)
+
+def calculate_keys(p, q, nbits):
+    """Calculates an encryption and a decryption key given p and q, and
+    returns them as a tuple (e, d)
+
+    """
+
+    n = p * q
+    phi_n = (p-1) * (q-1)
+
+    while True:
+        # Make sure e has enough bits so we ensure "wrapping" through
+        # modulo n
+        e = max(65537, rsa.prime.getprime(nbits/4))
+        if rsa.prime.are_relatively_prime(e, n) and rsa.prime.are_relatively_prime(e, phi_n):
+            break
+
+    (d, i, j) = extended_gcd(e, phi_n)
+
+    if not d == 1:
+        raise Exception("e (%d) and phi_n (%d) are not relatively prime" % (e, phi_n))
+    if (i < 0):
+        raise Exception("New extended_gcd shouldn't return negative values")
+    if not (e * i) % phi_n == 1:
+        raise Exception("e (%d) and i (%d) are not mult. inv. modulo phi_n (%d)" % (e, i, phi_n))
+
+    return (e, i)
+
+
+def gen_keys(nbits):
+    """Generate RSA keys of nbits bits. Returns (p, q, e, d).
+
+    Note: this can take a long time, depending on the key size.
+    """
+
+    (p, q) = find_p_q(nbits)
+    (e, d) = calculate_keys(p, q, nbits)
+
+    return (p, q, e, d)
+
+def newkeys(nbits):
+    """Generates public and private keys, and returns them as (pub,
+    priv).
+
+    The public key consists of a dict {e: ..., , n: ....). The private
+    key consists of a dict {d: ...., p: ...., q: ....).
+    """
+
+    nbits = max(9,nbits)           # Don't let nbits go below 9 bits
+    (p, q, e, d) = gen_keys(nbits)
+
+    return ( {'e': e, 'n': p*q}, {'d': d, 'p': p, 'q': q} )
+