question: private String sign ( String baseString , PrivateKey privateKey ) { try { Signature signer = Signature . getInstance ( SHA1_WITH_RSA ) ; signer . initSign ( privateKey ) ; signer . update ( baseString . getBytes ( UTF_8 ) ) ; return DatatypeConverter . printBase64Binary ( signer . sign ( ) ) ; } catch ( InvalidKeyException e ) { throw new MCApiRuntimeException ( e ) ; } catch ( SignatureException e ) { throw new MCApiRuntimeException ( e ) ; } catch ( UnsupportedEncodingException e ) { throw new MCApiRuntimeException ( e ) ; } catch ( NoSuchAlgorithmException e ) { throw new MCApiRuntimeException ( e ) ; } }
target:  Method to sign the signature base string.