Module: RSA::PKCS1

Defined in:
lib/rsa/pkcs1.rb

Overview

Support for the PKCS #1 (aka RFC 3447) padding schemes.

See Also:

Class Method Summary collapse

Class Method Details

.i2osp(x, len = nil) ⇒ String

Converts a nonnegative integer into an octet string of a specified length.

This is the PKCS #1 I2OSP (Integer-to-Octet-String) primitive. Refer to PKCS #1 v2.1 pp. 8-9, section 4.1.

Examples:

RSA::PKCS1.i2osp(9_202_000, 2)    #=> ArgumentError: integer too large
RSA::PKCS1.i2osp(9_202_000, 3)    #=> "\x8C\x69\x50"
RSA::PKCS1.i2osp(9_202_000, 4)    #=> "\x00\x8C\x69\x50"

Parameters:

  • x (Integer) —

    nonnegative integer to be converted

  • len (Integer) (defaults to: nil) —

    intended length of the resulting octet string

Returns:

  • (String) —

    octet string of length ‘len`

Raises:

  • (ArgumentError) —

    if ‘n` is greater than 256^len

See Also:



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# File 'lib/rsa/pkcs1.rb', line 26

def self.i2osp(x, len = nil)
  raise ArgumentError, "integer too large" if len && x >= 256**len

  StringIO.open do |buffer|
    while x > 0
      b = (x & 0xFF).chr
      x >>= 8
      buffer << b
    end
    s = buffer.string
    s.force_encoding(Encoding::BINARY) if s.respond_to?(:force_encoding)
    s.reverse!
    s = len ? s.rjust(len, "\0") : s
  end
end

.os2ip(x) ⇒ Integer

Converts an octet string into a nonnegative integer.

This is the PKCS #1 OS2IP (Octet-String-to-Integer) primitive. Refer to PKCS #1 v2.1 p. 9, section 4.2.

Examples:

RSA::PKCS1.os2ip("\x8C\x69\x50")  #=> 9_202_000

Parameters:

  • x (String) —

    octet string to be converted

Returns:

  • (Integer) —

    nonnegative integer

See Also:



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# File 'lib/rsa/pkcs1.rb', line 54

def self.os2ip(x)
  x.bytes.inject(0) { |n, b| (n << 8) + b }
end

.rsadp(k, c) ⇒ Integer

Recovers the message representative from a ciphertext representative under the control of a private key.

This is the PKCS #1 RSADP decryption primitive. Refer to PKCS #1 v2.1 pp. 10-11, section 5.1.2.

Parameters:

  • k (Key, #to_a) —

    RSA private key (‘n`, `d`)

  • c (Integer) —

    ciphertext representative, an integer between 0 and ‘n` - 1

Returns:

  • (Integer) —

    message representative, an integer between 0 and ‘n` - 1

Raises:

  • (ArgumentError) —

    if ‘c` is out of range

See Also:



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# File 'lib/rsa/pkcs1.rb', line 88

def self.rsadp(k, c)
  n, d = k.to_a
  raise ArgumentError, "ciphertext representative out of range" unless c >= 0 && c < n
  m = Math.modpow(c, d, n)
end

.rsaep(k, m) ⇒ Integer

Produces a ciphertext representative from a message representative under the control of a public key.

This is the PKCS #1 RSAEP encryption primitive. Refer to PKCS #1 v2.1 p. 10, section 5.1.1.

Parameters:

  • k (Key, #to_a) —

    RSA public key (‘n`, `e`)

  • m (Integer) —

    message representative, an integer between 0 and ‘n` - 1

Returns:

  • (Integer) —

    ciphertext representative, an integer between 0 and ‘n` - 1

Raises:

  • (ArgumentError) —

    if ‘m` is out of range

See Also:



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# File 'lib/rsa/pkcs1.rb', line 70

def self.rsaep(k, m)
  n, e = k.to_a
  raise ArgumentError, "message representative out of range" unless m >= 0 && m < n
  c = Math.modpow(m, e, n)
end

.rsasp1(k, m) ⇒ Integer

Produces a signature representative from a message representative under the control of a private key.

This is the PKCS #1 RSASP1 signature primitive. Refer to PKCS #1 v2.1 pp. 12-13, section 5.2.1.

Parameters:

  • k (Key, #to_a) —

    RSA private key (‘n`, `d`)

  • m (Integer) —

    message representative, an integer between 0 and ‘n` - 1

Returns:

  • (Integer) —

    signature representative, an integer between 0 and ‘n` - 1

Raises:

  • (ArgumentError) —

    if ‘m` is out of range

See Also:



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# File 'lib/rsa/pkcs1.rb', line 106

def self.rsasp1(k, m)
  n, d = k.to_a
  raise ArgumentError, "message representative out of range" unless m >= 0 && m < n
  s = Math.modpow(m, d, n)
end

.rsavp1(k, s) ⇒ Integer

Recovers the message representative from a signature representative under the control of a public key.

This is the PKCS #1 RSAVP1 verification primitive. Refer to PKCS #1 v2.1 p. 13, section 5.2.2.

Parameters:

  • k (Key, #to_a) —

    RSA public key (‘n`, `e`)

  • s (Integer) —

    signature representative, an integer between 0 and ‘n` - 1

Returns:

  • (Integer) —

    message representative, an integer between 0 and ‘n` - 1

Raises:

  • (ArgumentError) —

    if ‘s` is out of range

See Also:



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# File 'lib/rsa/pkcs1.rb', line 124

def self.rsavp1(k, s)
  n, e = k.to_a
  raise ArgumentError, "signature representative out of range" unless s >= 0 && s < n
  m = Math.modpow(s, e, n)
end